Posted inunclassified Chemical formula 2 Posted by By Agodirin October 14, 2024No Comments Report a question What's wrong with this question? You cannot submit an empty report. Please add some details. 3 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950 Created by Agodirin Chemistry: Chemical Formula 2 1 / 50 1. chem_formula57_A compound contains 37.% of cu and 41.7% of Cl and the rest is water of crystallization. What is the emperical formula ?[Cu=63.5, Cl=35.5 and H2O=18] A) CuCl3.2H2O B) CuCl.H2O C) CuCl2.2H2O D) CuCl2.H2O To calculate the empirical formula of a compound we need the number of moles of each of the elements in the compound. We get the number of moles by dividing the mass of the element by the molar mass or mass of one mole. Since we are given percentages and not the mass of each element we can assume that the mass is 100g of the compound which correspondst to 100%.So cu-37.1g, Chlorine will be 41.7g and the remaining is water (100-(41.7+ 37.1))=21.2g. So the number of moles of Cu = 37.1/63 = 0.58moles, and for chlorine will be 41.7g/35.5g =1.2mol and for water will be 21.2/18=1.2. To get the ratios of the elements will divide by the lowest . so 0.58/0.58 for copper = 1 . for chlorine 1.2/0.58=, to nearest whole number is 2 and and 1.2/0.58 for water is 2 . so the simplest ratio of the combining elements is 1:2:2 hence CuCl2.(H2O)2 which is CuCl2.2H2O 2 / 50 2. chem_formula61_What is the molecular mass of an organic compound with emperical formula of CH2O [C=12, O=16, H=1] A) 125 B) 45 C) 42 D) 180 Molecular formula or (Molecular mass)/ emperical formula or (emperical mass)=n. the mass of the emperical will be (12 +2+16=30). x/CH2O= n and /30=n. the molecullar mass of the substance has to be a simple multiple of the emperical mass hence the likely answer is 180 giving a molecular formula rof 180/30=6 and 6 x CH2O = C6H12O6 . not here that the information given by the question is not enough to directly solve for the answer but since we know that the molecular mass should be a simple multiple of the emperical mass we need to identify whether the molecular formula is a multiple of the empirical formula. The molecular formula can be derived from the empirical formula by multiplying it by a whole number n n so we divide each of the options by 30 and see which one give a whole number . only 180 gives whole number of 6 hence that is the likely answer here 3 / 50 3. chem_formula96_What is the amount of sulphur(IV) oxide required to deposit 12g of of sulphur on reacting with excess hydrogen sulphide A) 4g B) 8g C) 12g D) 16g First is to get the correct balanced equation. First Hydrogen sulphide is H2S and sulphur Iv oxide . sulpur oxidation number is 4 and oxygen is -2 so two atoms of oxygen will be required in sulphur Iv oxide , giving SO2. Now get the balanced equation: 2H2S+ SO2= 3S + 2H2O, then based on the equation determine the stoichiometry i.e the number of mols of each element of compound. So 2 mole of H2S combines with 1 mole of SO2 to give 3 moles of sulphur and 2 moles of water. So based on this 1 mole of SO2 gives 3 moles of sulphur . how many moles of Sulphur is in 12g : 12/32= 0.375. so if one mole of sulphur IV oxide gives 3 moles of Sulphur how many moles of sulphur IV oxide will give 0.375 moles of sulphur: 0.375/3=0.125. now get the gram of so2. Molar mass is 64 hence g of 0.125mol will be 0.125x64=8g 4 / 50 4. chem_formula76_The molar mass of carbon is 12g and the molar mass of oxygen is 16g . Which of the following is correct A) carbon is heavier than oxygen B) oxygen and carbon have similar weight C) the number of atoms in 12g of carbon is same as the number of atoms in 16 of oxygen D) the number of atoms in one of oxygen is one and half times the number of atoms in one mole of carbon The molar mass of carbon is 12 g, while the molar mass of oxygen is 16 g. Therefore, oxygen is heavier than carbon. The molar masses are different (12 g for carbon and 16 g for oxygen), so they do not have similar weights. However The number of atoms in 12 g of carbon is the same as the number of atoms in 16 g of oxygen. Since 1 mole of any substance contain same avodagro number of particles regardless of the molar mass 5 / 50 5. chem_formula80_what is the mas of 0.105 mol of Na2Co3.10H2O [H=1, C=12,O=16,Na=23] A) 60.6g B) 15.01g C) 30.3g D) 105g First, calculate the molar mass of NaโCOโยท10HโO.[(23 x2) + 12 +(16x3) + (10x18)]. So the compound weighs 288g per mol. Now what is the wiegth of 0.105mol. That will be mass of one mol x 0.105 = 30.3g 6 / 50 6. chem_formula58_Which of the following is correct about the relationship between molecular and emperical formula in solving chemical formula and equation A) emperical formula multiplied by 0.3 equals molecular formula B) emperical formula multiplied by molecular formula equals whole number n C) molecular formula divided by emperical formula equals whole number n D) emperical formula divided by molecular formula equals a whole number n To understand the relationship between empirical formulas and molecular formulas, let's clarify their definitions: Empirical Formula: The simplest whole-number ratio of the elements in a compound. Molecular Formula: The actual number of atoms of each element in a molecule of the compound. Correct Statement The correct relationship is: Molecular formula divided by empirical formula equals a whole number n. Explanation, Molecular Formula / Empirical Formula = Whole Number n: This means that the molecular formula is a multiple of the empirical formula. If the empirical formula represents the simplest ratio of elements, the molecular formula can be obtained by multiplying the empirical formula by a whole number n 7 / 50 7. chem_formula66_Which of the following terms indicates the number of bonds that can be formed by an atom A) atomic number B) oxidation number C) electronegativity D) valence Valence refers to the ability of an atom to bond with other atoms, which is determined by the number of electrons in its outer shell (valence shell). It indicates how many bonds an atom can form. For example, carbon has a valence of 4, allowing it to form four bonds. Oxidation Number:Definition: The oxidation number (or oxidation state) represents the charge of an atom in a compound and indicates the degree of oxidation (loss of electrons) of that atom. Importance: While it can give insight into how many electrons an atom can gain or lose, it does not directly indicate the number of bonds it can form. Atomic Number: Definition: The atomic number is the number of protons in the nucleus of an atom, which defines the element. Importance: It does not provide information about bonding capabilities. Electronegativity: Definition: Electronegativity is a measure of an atom's ability to attract and hold onto electrons when it is part of a compound. Importance: It influences bond polarity but does not directly indicate the number of bonds that can be formed 8 / 50 8. chem_formula62_A gaseous metallic chloride MCl consist of 20.22% of M by mass, the molecular formula is [M-27, Cl-35.5] A) M2Cl3 B) MCl3 C) M2Cl D) MCl2 Let's break down the problem using the concept of combining moles and ratios, which can help clarify how we arrive at the molecular formula. Given Information: The metal M has an atomic mass of 27 g/mol, the chlorine (Cl) has an atomic mass of 35.5 g/mol. The compound consists of 20.22% by mass.. so assuming that the mass of the element is 100g. Step 1: Set Up the Mass Ratio: Let's denote: The formula of the compound MxClx. Step 2: Calculate the Total Molar Mass: Assume the total mass of the compound is 100 g since we were not given hence mass of M will be = 20.22 g and mass of Cl will be = 100 g - 20.22 g = 79.78 g. Step 3: Calculate Moles of Each Element. Calculate moles of M , ย M=20.22โg/27โg/molโ0.749โmoles. Calculate moles of Cl: Molesย ofย Cl=79.78โg/35.5โg/molโ2.25โmoles. Step 4: Determine the Mole Ratio by Dividing both by the smallest number of moles: Ratioย ofย M=0.749/0.749=1 and Ratioย ofย Cl=2.25/0.749โ3 . Step 5: Write the Molecular Formula From the mole ratio: For every 1 mole of M, there are approximately 3 moles of Cl. Thus, the empirical formula is: MCl3 9 / 50 9. chem_formula83_what type of reaction is this 2HgO(s) = 2Hg(l) + O2(g) A) replacement B) decomposition C) oxidation D) combustion Decomposition Explanation: A decomposition reaction occurs when a single compound breaks down into two or more products. Here, mercuric oxide decomposes into mercury and oxygen. Other Options:Replacement: Not applicable; no elements are replacing one another. Combustion: Involves a substance reacting with oxygen, which does not describe this reaction. Oxidation: While oxygen is produced, the reaction is primarily a decomposition 10 / 50 10. chem_formula72_which of the following is not correct about the naming convention for acids containing oxygen or oxoacids A) the oxygen is named first as oxo B) the number of oxygen atom is include as mono(1) or di(II) etc C) the central atom in the compound is named with ending -ate such as cromate, sulphate etc D) the word base is added as the last In the naming of acids, the term "base" is not used. Instead, the name of the acid is typically followed by the word "acid" (e.g., sulfuric acid, nitric acid). 11 / 50 11. chem_formula56_Find the emperical formula for an oxide of iron containing 79% iron[F3=66,O=16]. A) FeO B) Fe2O4 C) FeO3 D) Fe3O To calculate the empirical formula of a compound we need the number of moles of each of the elements in the compound. We get the number of moles by dividing the mass of the element by the molar mass or mass onf one mole. Since we are given percentages and not the mass of each element we can assume that the percentage is 100g of the compound so each of the percentages can be taken as grams. so containing 70% iron(Fe) will be 70g, and 30% oxygen (O) will be 30g. so we this we calculate the number of mole of each by dividing the grams by the molar mass. For Fe 70/56g, and and oxygen will be 30g/16g so the number of moles Fe and oxygen will be 1.41 and 1.31 respectively. To get the ratios of the elements will divide by the lowest . so 1.41/1.31 so the ratio for Fe is 1.07, to nearest whole number is 1 and and 1.31/1.31 for oxygen is 1 . so the simplest ratio of the combining elements is 1:1 hence FeO 12 / 50 12. chem_formula77_How many atoms of Fe are present in 1 mole [molar mass of Fe is 65g] A) 6.022ร1023 B) 65 atoms C) 3.011 x 1023 D) 12.044 x 1023 1 mole contains avogadro's number of particles or atoms 13 / 50 13. chem_formula71_Acids that contain oxygen atoms are called A) oxoacid B) monoxide C) diacid D) hydroxide Monoxide: This term refers to a compound containing one oxygen atom, but it is not related to acids. Oxoacid: Correct. An oxoacid is an acid that contains oxygen, hydrogen, and another element (usually a nonmetal). Examples include sulfuric acid (H2SO4, and nitric acid (HNO3), Hydroxide: This term refers to a compound containing the hydroxyl group (OHโ), such as sodium hydroxide (NaOH), and is not specifically an acid that contains oxygen. Diacid: This term generally refers to an acid that can donate two protons (Hโบ ions), such as sulfuric acid (H2SO4). While diacids may contain oxygen, the term does not specifically denote that oxygen is present. 14 / 50 14. chem_formula99_Howย manyย molesย ofย Hโย areย neededย toย completelyย reactย withย 3ย molesย ofย Nโย toย formย NHโ?ย N2+H2โNH3 A) 6 B) 4 C) 3 D) 9 Explanation: Theย balancedย equation:ย N2+3H2โ2NH3. Eachย moleย ofย N2ย needsย 3ย molesย ofย H2. Forย 3ย molesย ofย N2,ย youย needย 3ร3=9ย molesย ofย H2. 15 / 50 15. chem_formula91_In a reaction between compounds A and B, a new substance C is formed and there is remnant of B. which of the following is correct A) A is dominant B) B is dominant C) A is a limiting reactant D) B is a limiting reactant Limiting Reactant Concept: The limiting reactant is the substance that is entirely consumed first in a chemical reaction, thus limiting the amount of product that can be formed. In this scenario, if there is a remnant of B after the reaction, it indicates that A was completely consumed. Once A is used up, the reaction stops, leaving excess B. Therefore, since A was consumed completely before B, A is indeed the limiting reactant 16 / 50 16. chem_formula92_What is the amount of sulphur(IV) oxide required to deposit 12g of of sulphur on reacting with excess hydrogen sulphide A) 1mol of SO2 B) 0.25 mol of SO2 C) 2.5mol of SO2 D) 0.125 mol of SO2 First is to get the correct balanced equation. First Hydrogen sulphide is H2S and sulphur Iv oxide . sulpur oxidation number is 4 and oxygen is -2 so two atoms of oxygen will be required in sulphur Iv oxide , giving SO2. Now get the balanced equation: 2H2S+ SO2= 3S + 2H2O, then based on the equation determine the stoichiometry i.e the number of mols of each element of compound. So 2 mole of H2S combines with 1 mole of SO2 to give 3 moles of sulphur and 2 moles of water. So based on this 1 mole of SO2 gives 3 moles of sulphur . how many moles of Sulphur is in 12g : 12/32= 0.375. so if one mole of sulphur IV oxide gives 3 moles of Sulphur how many moles of sulphur IV oxide will give 0.375 moles of sulphur: 0.375/3=0.125 17 / 50 17. chem_formula59_Which of the following is correct about the relationship between molecular and emperical formula in solving chemical formula and equation A) the molecular formula is a simple multiple of emperical formula B) the emperical formula is a simple multiple of molecular formula C) the molecular formula is one-third the emperical formula D) the molecular formula and emperical formula are one and the same The molecular formula is a simple multiple of the empirical formula: The molecular formula represents the actual number of atoms of each element in a molecule, while the empirical formula shows the simplest whole-number ratio of these elements. The molecular formula can be obtained by multiplying the empirical formula by a whole number 18 / 50 18. chem_formula69_which of the following is not correct about compounds A) a compound containing four element is quarternary compound B) A compound containing five element is monoxide C) a compound containing three elements is tertiary compound D) a compound containing two elements is binary compound The term "monoxide" specifically refers to a compound containing one oxygen atom and one other element (e.g., carbon monoxide, COtext{CO}CO). A compound containing five elements does not have a special nomenclature like "monoxide." 19 / 50 19. chem_formula95_write the balanced equation for hydrogen sulphite reacting with sulphur IV oxide to librate Sulphur A) H2S+ SO2= 3S + 2H2O B) 2H2S+ SO2= 3S + H2O C) 2H2S+ SO2= 3S D) 2H2S+ SO2= 3S + 2H2O First is to get the correct balanced equation. First Hydrogen sulphide is H2S and sulphur Iv oxide . sulpur oxidation number is 4 and oxygen is -2 so two atoms of oxygen will be required in sulphur Iv oxide , giving SO2. Now get the balanced equation: 2H2S+ SO2= 3S + 2H2O 20 / 50 20. chem_formula81_Calculate the number of silver atoms in pure silver bracelet tha has a mass of 35g [ag=108, Avogadro constant 6.02 x1023 ] A) 1.95 x1021 B) 1.95 x1023 C) 5.52 x1023 D) 3.25 x1021 First, find the number of moles of silver: number of moles = mass/molar mass: 35/108=0.324mol. we know that one mole contains avogadroโs number of atoms (6.02 x 1023) so 0.324mols will contain 0.324 muliplied by the avogadroโs number = 1.95 x1023 21 / 50 21. chem_formula73_What is the correct IUPAC name for NO2- A) trioxonitrate(IV)ion B) Trioxonitrate(III) ion C) Dioxonitrate(IV) ion D) Dioxonitrate(III) ion What is the correct IUPAC name for NO2-. This is a oxoacid with two oxygen atoms so its name starts with dioxo. The main atom here is nitrogen which ends with -ate; Nitrate. So it is dioxonitrate. Now to determine the oxidation number of the nitrogen which will be added to the name. to get the oxidation number we know the the sum of all the oxidation number must be equal to the charge on the compound. So x +(2 oxygen)=-1. And oxidation number of one oxygen is -2 so two will be -4 hence x+(-4)=-1 and x will be equal to 4-1 so it is 3 . so the name is dioxonitrate(III) ion 22 / 50 22. chem_formula79_what is the molar mass of a substance in mol/g if 0.4mol is 25g A) 2.5 B) 100 C) 62.5 D) 6.3 Answer: 62.5 g/mol. Explanation: Molar mass is calculated using the formula: Molar Mass=mass (g) divided by the number of moles (mol). Substituting the values: Molar Mass=25โg/0.4โmol=62.5โg/mol 23 / 50 23. chem_formula84_what type of reaction is this Zn(s) + CuSO4(aq) = ZnSO4(aq) + Cu(s) A) replacement B) displacement C) decomposition D) combustion Displacement. Explanation: A displacement reaction occurs when one element displaces another in a compound. Here, zinc displaces copper from copper sulfate. Other Options: Replacement: This could describe the same concept, but "displacement" is more specific to single-element displacement. Decomposition: Not applicable; no compounds are breaking down. Combustion: Not applicable; there is no reaction with oxygen 24 / 50 24. chem_formula98_Balanceย theย equation:ย Na+H2OโNaOH+H2.ย Whichย ofย theย followingย isย correct? A) Na+2H2OโNaOH+2H2 B) 2Na+2H2Oโ2NaOH+H2 C) 2Na+H2Oโ2NaOH+2H2 D) Na+H2Oโ2NaOH+H2 Correctย equation:ย 2Na+2H2Oโ2NaOH+H2 Explanation: Sodiumย atoms:ย 2ย onย bothย sides. Hydrogenย atoms:ย 4ย onย bothย sidesย (2ย fromย H2Oย andย 2ย fromย H2). Oxygenย atoms:ย 2ย onย bothย sides 25 / 50 25. chem_formula94_What is the formula for sulphur(IV)oxide A) SO4 B) S4O C) S2O D) SO2 These are the steps to take when writing a chemical formula. 1) Determine Charge: Check if the compound should be neutral (most common) or if it's an ion (charged particle). 2) Identify Oxidation Numbers: Know the typical oxidation states of the elements involved. 3) Balance Charges: Combine the elements in a ratio that makes the total charge of the compound zero (for neutral compounds) or matches the specified charge (for ions). So for this question: For example, in Sulphur (IV) has an oxidation number of +4. Oxygenhas an oxidation number of -2 . So to balance the oxidation numbers they combine such as two atoms of oxygen will give -4 to balance the +4 on they combine in a 1:2 ratio to balance out to zero. When balancing the charges and chemical equation remember that In essence, itโs like a puzzle where all pieces must fit perfectly to achieve stability. Alterativelly we can say S4+ combines with O2- . remove the charges and exchange their oxidation numbers so S2O4 . now take this to the smallest ratio by dividing by 2 hence it becomes S1O2 which is SO2. The formula for sulphur(IV) oxide is SOโ. This compound is also known as sulfur dioxide, which is a gas with a pungent, suffocating odor, often associated with volcanic activity. 26 / 50 26. chem_formula64_which of the following is not correct about oxidation number A) The oxidation number of a monatomic ion is equal to its charge. B) the sum of oxidation number of atoms in a neutral compound is zero C) alkaline earth metals have oxidation number of +2 D) Group 7 elements have oxidation number of +7 Group 7 elements (halogens) typically have an oxidation number of -1 when they are in compounds, although they can have positive oxidation states (such as +1, +3, +5, +7) in certain compounds. However, it is incorrect to state that they always have an oxidation number of +7. 27 / 50 27. chem_formula70_which of the following is not correct about the naming convention for a binary compount ( a compound containing two elements) A) the name of the non-metal comes after the name of the metal B) the name of the metal ends with -ide C) the name of the metal comes first D) exceptions to name ending in ide is H2O which is water The name of the metal comes first: In a binary compound, the metal (usually a cation) is named first, followed by the non-metal (anion). The name of the non-metal comes after the name of the metal: This is consistent with the naming convention for binary compounds, where the non-metal is named after the metal. The name of the metal ends with -ide: Not Correct. The name of the metal does not typically end with -ide. Instead, the non-metal's name is modified to end with -ide. For example, in sodium chloride (NaCltext{NaCl}NaCl), sodium is the metal, and it remains "sodium," while chlorine becomes "chloride.". Exceptions to name ending in -ide is H2O, which is water, ammonium(NH4+) and phosphine (Ph3) 28 / 50 28. chem_formula52_The emperical formula for benzene (C6H6) is A) C3H3 B) C2H2 C) CH D) C2H to get the simplest ration divide the lowerest subscript by all the other subscript and itself and convert to nearest whole number 29 / 50 29. chem_formula78_how many atoms are present in 130g of Fe [ molar mass of Fe=65g] A) 130 atoms B) 6.022ร1023 C) 12.044 x 1023 D) 3.011 x 1023 To find the number of atoms in 130 g of iron (Fe) given that the molar mass of Fe is 65 g/mol, follow these steps: Step Calculate the number of moles Using the formula: Numberย ofย moles=massย (g)/molarย massย (g/mol). Substituting the values: 130/65= 2moles . and 1 mole contains avogadros number of fe atoms so 2 moles will contain 2 x avogadros number = 2 x (6.022ร1023)= 12.044 x 1023 or 1.2044 x 1024 30 / 50 30. chem_formula53_The emperical formula for Glucose (C6H12O6) is A) C3H2O3 B) C3H2O C) C1H2O1 D) CHO to get the simplest ration divide the lowerest subscript by all the other subscript and itself and convert to nearest whole number 31 / 50 31. chem_formula90_When 21g of iron filing and 15g of powdered sulphur are head, Yg of iron(II) sulphide was obtained . Which reactant is in excess and by how much? A) Sulphur in excess by 5g B) Sulphur in excess by 3 g C) Iron filings in excess by 5g D) Iron filling in excess by 3g Ans= Sulphur is in excess of 3g . The reaction between iron and sulfur to form iron(II) sulfide (FeS) can be represented as:. Fe+S= FeS. Since the oxidation number of Fe is 2 and the valency fo sulphur is -2 the two cancel out hence the compound formed is one atom of Fe combines with one atom of S to form one mole of FeS. . Molar mass of Fe: 56 g/mol and Molar mass of S: 32 g/mol. So the number of moles of Fe will be Moles of Fe: 21โg/56โg/molโ0.375mol and the number of moles of S will be 15โg/32โg/molโ0.469โ. The stoichiometry of the reaction shows a 1:1 ratio. Thus:Iron is the limiting reactant (0.375 mol), and sulfur is in excess. So we substract the limiting reactant value from the higher concentrated reactant 0.469 -0.375= 0.094mol. Now the excess g will be mol x molar mass = 0.094 x 32 = 3.0g 32 / 50 32. chem_formula60_A hydrocarbon contains 80% carbon by mass. If the relative moleclar mass of the hydrocarbon is 30, what is the molecular mass of the hydrocarbon [C=12, H=1] A) C3H6 B) CH3 C) C2H6 D) C4H10 Hydrocarbon contains Carbon and Hydrogen. CH. If the hydrocarbon is 80% C then the remaining 20% is H. so assuming the hydrocarbon is 100g the carbon is 80g and the hydrogen is 20g. so the emperical formula is 80/12 (6.6) for carbon and 20/1 (20) for hydrogen. To ge the ratio of carbon and hydrogen, we divide by the lowest so 6.6/6.6 =1 and 20/6.6=3. So the emperical formula is C1H3 (CH3). Now that we know the emperical formula and the mass of one mole ( the molecular mass) we can solve for the molecular formula using the equation : molecular formula/emperical formula =n because the division of the molecular mass by the emperical mass will also give n. if the emperical formula is CH3 then the mass will be 12+ 3 = 15. . so the n will be 30/15=2 . . so molecular formula = 2 x CH3= C2H6 33 / 50 33. chem_formula87_A substance which changes the rate of a chemical reaction without being used up in the reaction is A) catalyst B) active C) inactive D) resilient A catalyst speeds up a reaction without being consumed in the process, allowing it to be used repeatedly 34 / 50 34. chem_formula75_Which of the following is correct. If molar mass of element A is 2g and Molar mass of element B is 3g then A) the number of particles in 1 mole of element B is more than the number of particles in 1 mole of element A B) the weight of one mole of element A is equal to the weight of one mole of element B C) the number of particles in 1 mole of element A is same as the number of particles in 1 mole of element B D) element A is heavier than element B By definition, 1 mole of any substance contains 6.022ร1023 particles (Avogadro's number). Therefore, the number of particles is the same for both 35 / 50 35. chem_formula74_Which of the following has the largest mass of the same substance A) 1 molecule B) 1 atom C) one ion D) 1 mole 1 mole: Contains approximately 6.022ร10236.022 times 10^{23}6.022ร1023 particles (Avogadro's number). The mass of 1 mole of a substance is equal to its molar mass (in grams). 1 molecule: The mass of a single molecule varies based on the substance, but it is significantly smaller than a mole. 1 atom: Similar to a molecule, the mass of a single atom depends on the element. It is measured in atomic mass units (amu), with 1 amu being about 1.66ร10โ271.66 kg. 1 ion: Like an atom, the mass of a single ion also depends on the element and its charge, but it is usually similar to that of its corresponding atom. 1 mole has the largest mass because it contains a vast number of particles (about 6.022ร1023, making its mass equal to the molar mass of the substance in grams, which is significantly larger than the mass of a single atom, molecule, or ion 36 / 50 36. chem_formula55_Calculate the emperical formul of a compound containg 43.4% sodium, 11.3% carbon and 45.3% oxygen. [Na-23, O=16 , c=12] A) Na3CO3 B) Na2CO4 C) Na2CO3 D) NaCO3 To calculate the empirical formula of a compound we need the number of moles of each of the elements in the compound. We get the number of moles by dividing the mass of the element by the molar mass or mass onf one mole. Since we are given percentages and not the mass of each element we can assume that the percentage is 100g of the compound so each of the percentages can be taken as grams. so containing 43.4% sodium (Na) will be 43.4g, 11.3% carbon (C) will be 11.3g and , and 45.3% oxygen (O) will be 45.3g. so we this we calculate the number of mole of each by dividing the grams by the molar mass. Sodium 43.4g/23g, Carbon will be 11.3g/12g and oxygen will be 45.3g/16g so the number of moles of sodium, Carbona and oxygen will be 1.89, 0.94 and 2.83 respectively. To get the ratios of the elements will divide by the lowest . so sodium ration will be 1.98/0.94 = 2.0, for carbon it will be 0.94/0.94= 1.0 and for oxygen will be 2.83/0.94=3 . so the simplest ratio of the combining elements is 2:1:3. Na2C1O3 = Na2CO3 37 / 50 37. chem_formula68_What is the oxidation number of boron in Na[B(NO3)4] A) 2 B) 1 C) 4 D) 3 Na is metal with oxidation umber of 1, B is x and NO3- is 4 so NO3 charge will be -1 x 4= -4. The total compound is neutral ie the charge is zero. So Na charge+ boron charge+ nitrate charge=0. So 1+x+(-4)= 0 , x-3=0 and x=3 38 / 50 38. chem_formula89_Which of the following is not a characteristic of catalysts A) catalystreaction are specific B) Catalysts can be re-used after the reaction C) small quantity of catalysts speed up reaction between large quantity of reactants D) catalyst are changed to new substances after the chemical reaction Answer: Catalysts are changed to new substances after the chemical reaction Explanation: Catalysts remain unchanged at the end of a reaction and can be reused. Other Options: Small quantity of catalysts speed up reaction between large quantities of reactants: This is true; catalysts work in small amounts. Catalysts are specific: This is correct; many catalysts work for specific reactions. Catalysts can be re-used after the reaction: True; catalysts are not consumed 39 / 50 39. chem_formula97_Whichย coefficientย correctlyย balancesย theย followingย equation?ย C3H8+O2โCO2+H2O A) C3H8+4O2โ3CO2+3H2O B) C3H8+6O2โ3CO2+4H2O C) C3H8+3O2โ3CO2+4H2O D) C3H8+5O2โ3CO2+4H2O Correctย equation:ย C3H8+5O2โ3CO2+4H2O. Explanation: Carbonย atoms:ย 3ย onย bothย sides.Hydrogenย atoms:ย 8ย onย bothย sides. Oxygenย atoms:ย 10ย onย reactantย sideย (5ร2)ย andย 10ย onย productย sideย (3ร2+4) 40 / 50 40. chem_formula100_Whatย isย theย correctย coefficientย forย HClย whenย balancingย theย equation:ย Zn+HClโZnCl2+H2? A) 3 B) 2 C) 1 D) 4 Correctย equation:ย Zn+2HClโZnCl2+H2. Explanation: Zincย atoms:ย 1ย onย bothย sides. Chlorineย atoms:ย 2ย onย bothย sides. Hydrogenย atoms:ย 2ย onย bothย sides 41 / 50 41. chem_formula88_A reaction in which the rate of forward or backward direction is determined only by temperature is A) endothermic reaction B) catalysed reaction C) exothermic reaction D) thermal dissociaton reaction Thermal dissociation reaction, Explanation: A thermal dissociation reaction can be influenced by temperature changes, affecting the rates of forward and reverse reactions. Other Options: Catalysed reaction: Involves catalysts that change the rate but are not solely temperature-dependent. Exothermic reaction: This type of reaction releases heat but does not necessarily relate to the forward or backward direction specifically. Endothermic reaction: This absorbs heat but also does not define the rate dependency 42 / 50 42. chem_formula51_The emperical formula for ethane (C2H6) is A) CH3 B) C2H C) CH D) CH2 to get the simplest ration divide the lowerest subscript by all the other subscript and itself and convert to nearest whole number 43 / 50 43. chem_formula93_what is the chemical formula for iron(II) sulphide A) FeS B) Fe2S C) Fe2S3 D) FeS2 These are the steps to take when writing a chemical formula. 1) Determine Charge: Check if the compound should be neutral (most common) or if it's an ion (charged particle). 2) Identify Oxidation Numbers: Know the typical oxidation states of the elements involved. 3) Balance Charges: Combine the elements in a ratio that makes the total charge of the compound zero (for neutral compounds) or matches the specified charge (for ions). So for this question: For example, in FeS: Iron(II) has an oxidation number of +2. Sulfur has an oxidation number of -2 since its group 6 or 16. So to balance the oxidation numbers they combine They combine in a 1:1 ratio to balance out to zero. FeS 44 / 50 44. chem_formula82_what type of reaction is this H2(g) + Cl2(g) = 2HCl(g) A) replacement reaction B) displacement reaction C) combination reaction D) combustion reaction Combination reaction: Explanation: A combination reaction occurs when two or more substances combine to form a single product. Here, hydrogen and chlorine combine to form hydrogen chloride 45 / 50 45. chem_formula65_Determin the oxidation number of iodine in IO3 - A) -3 B) 3 C) -7 D) 5 To determine the oxidation number of iodine in the ion IO3โ(iodate ion), follow these steps: Step 1: Assign Known Oxidation Numbers, Oxygen (O) typically has an oxidation number of -2. Step 2: Set Up the Equation : Let the oxidation number of iodine (I) be x. and there are three oxygen atoms, each with an oxidation number of -2 each. Step 3: Write the Equation The sum of oxidation numbers in the ion must equal the charge of the ion, which is -1: so x+3(โ2)=โ1 . Step 4: Simplify the Equation : xโ6=โ1. Step 5: Solve for x, x= +5 46 / 50 46. chem_formula67_What is the oxidation number of X in X2O72- A) 8 B) -5 C) 6 D) -4 The total charge on the compound is -2. There are 2 atoms of X and 7 atoms of oxygen. The oxidation number of oxygen is -2 and that of X is unknown so the equation: the oxidation number of all the atoms in the compound add up to the total charge ofn the compound. Oxidation number of X is x and there are two (2x), and oxidation number of oxygen is -2 and therer are 7 , hence -14. So 2x +(-14)=-2. So 2x=12 and x= 6 47 / 50 47. chem_formula63_which of the following is not correct about oxidation number A) the oxidation number of halogens is -1 B) the oxidation number of oxygen is -2 C) the oxidation number of hydrogen is +1 D) the oxidation number of group one elements is +2 The oxidation number of alkali metals (Group 1 elements) is +1, not +2. 48 / 50 48. chem_formula54_How many moles of carbon are present in 56g of C particle (C=12) A) 4.7 B) 6.8 C) 68 D) 47 To calculate the number of moles of carbon in 56 grams, you can use the formula, we divide the 56g by the mass of one mole. The mass of one mole is 12 so the. Given: Mass of carbon (C) = 56 g and Molar mass of carbon (C) = 12 g/mol. The number of moles is 4.7 49 / 50 49. chem_formula86_A reaction which can proceeds forward or backwards under different conditions of temperature and pressure A) reversible B) double decomposition C) replacement D) Oxidation-Reduction Explanation: Reversible reactions can proceed in both the forward and reverse directions depending on conditions, such as temperature and pressure. Other Options: Double decomposition: This describes a specific type of reaction, not the general behavior of reactions under varying conditions. Replacement: Refers to a specific type of reaction where one element replaces another. Oxidation-Reduction: This involves electron transfer and does not imply reversibility in the general sense 50 / 50 50. chem_formula85_A reaction in which two compounds react to produce two different compounds is A) displacement B) oxidation C) double decomposition D) decomposition A reaction in which two compounds react to produce two different compounds is: Explanation: A double decomposition (or double displacement) reaction involves the exchange of ions between two compounds, resulting in the formation of two new compounds. Other Options: Decomposition: This involves a single compound breaking down into two or more simpler substances, not two compounds reacting. Displacement: This typically refers to one element replacing another in a compound. Oxidation: This is a reaction involving the loss of electrons, not specifically related to two compounds forming different compounds Your score is LinkedIn Facebook Twitter VKontakte Restart quiz Thank you Send feedback Share via: Facebook X (Twitter) LinkedIn More Agodirin View All Posts Post navigation Previous Post Respiration 1Next PostBiology: Excretion