Posted inunclassified Chemical Formula Vol 1 Posted by By Agodirin October 5, 2024 Report a question What's wrong with this question? You cannot submit an empty report. Please add some details. 10 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950 Created by Agodirin Chemistry: Chemical Formula 1 1 / 50 1. chem_formula45_Two elements Z and X combine forming a compound. If Z is a non-metal with valency of 2 and X is a metal with valency of 1 what is the chemical formula of the compound formed A) ZX2 B) X2Z C) Z2X D) 2XZ the simbol of the metal comes infront hence we have XZ the we exchage their valency and write is to the right and below X2Z1 2 / 50 2. chem_formula47_Which of the following is the appropriate chemical formula for calcium hydroxide A) CaCO3 B) CaO2H2 C) Ca(OH)2 D) Ca2C2OH2 alcium hydroxide is composed of one calcium ion (Ca²⁺) and two hydroxide ions (OH⁻). Therefore, the correct formula is Ca(OH)₂. 3 / 50 3. chem_formula30_how many hydrogen atoms are present in (NH4)2C2O2 A) 12 B) 8 C) 2 D) 4 In the formula (NH₄)₂C₂O₂, there are two ammonium ions (NH₄⁺): Each NH₄ has 4 hydrogen atoms, so: 2×4=8 hydrogen atoms 4 / 50 4. chem_formula9_Which of the following is not correct about covalent bond A) the number of electrons contributed by an atom is equal to its valency B) the number of covalent bonds is equal to the valency of the combining atoms C) the shared electron is totally donated to one of the atoms D) an atom contributes the number of electrons required for it to form a duplet or octet An atom contributes the number of electrons required for it to form a duplet or octet. Atoms will share or contribute electrons to achieve a stable electron configuration . The number of electrons contributed by an atom is equal to its valency. This statement is correct. The valency of an atom indicates the number of electrons it can share or bond with other atoms. The number of covalent bonds is equal to the valency of the combining atoms. The number of covalent bonds an atom can form is generally equal to its valency, as it indicates how many electrons it can share with other atoms.. The shared electron is totally donated to one of the atoms. This statement is not correct. In a covalent bond, electrons are shared between the atoms rather than one atom completely donating the electrons to another. This sharing defines the nature of covalent bonding 5 / 50 5. chem_formula37_What is the percentage composition by mass of Ca in CaO [Ca=40, O=16] A) 28.60% B) 32.50% C) 71.40% D) 64.8& To find the percentage composition by mass of calcium (Ca) in calcium oxide (CaO), we can use the following formula: the relative molar mass of the element divided by the relative molar mass of the compound multipled by 100. (Mass of the element in the compound/Molar mass of compoud)x 100 6 / 50 6. chem_formula24_Which of the following is not correct about one molecule of water(H2O) A) one atome of oxygen B) there are two molecules of hydrogen present C) the atomicity is three D) the emperical formula is H2O In one molecule of water (H₂O), there are two atoms of hydrogen, not two molecules. 7 / 50 7. chem_formula1_An element R with atomic number 3 and another element Q with atomic number 8 undergo a chemical reaction. Which of the following is correct A) Q is a group 8 element B) R has valency of 3 C) Q has valency of 7 D) R is the metal Characteristics of Element R (Atomic Number 3). Position in the Periodic Table: Elements with low atomic numbers (like 1, 2, and 3) are typically found on the left side of the periodic table, where metals are located. Since R has an atomic number of 3, it falls into this category.common Properties of Metals: Luster: Metals generally have a shiny appearance. While the question doesn't specify, it is a common characteristic of metals. Malleability and Ductility: Metals are known to be malleable (can be hammered into sheets) and ductile (can be drawn into wires). Although the question does not directly state this, it is a typical property of metals. Reactivity: Metals often react with nonmetals, especially in groups like the alkali metals (Group 1). Since R is likely to react with another element (Q with atomic number 8), it suggests that R behaves like a metal that can participate in chemical reactions. Valency: The question indicates that R has a valency (likely to lose electrons), which is typical for metals. Metals generally have lower electronegativities and tend to lose electrons easily to form positive ions 8 / 50 8. chem_formula46_Two elements Z and X combine forming a compound. If Z is a non-metal with valency of 3 and X is a metal with valency of 2 what is the chemical formula of the compound formed A) X3Z2 B) Z3X2 C) X2Z3 D) Z2X3 9 / 50 9. chem_formula39_If atom has electronic configuration of 1s2-2s2-2p3, what is the valence electron A) 3 B) 5 C) 8 D) 2 this is the number of electrons in the outermost shell 10 / 50 10. chem_formula31_what is the atomicty of (NH4)2C2O2 A) 10 B) 14 C) 8 D) 12 To determine the atomicity of (NH4)2C2O2, we need to calculate the total number of atoms in the formula. Breakdown of the Formula (NH4)2C2O2. Ammonium (NH4). There are 2 ammonium ions: (NH4)2. Each ammonium ion contains 1 nitrogen (N) and 4 hydrogens (H). Total from ammonium: Nitrogen: 2×1=2. Hydrogen: 2×4=8. Carbon (C) There are 2 carbon atoms: C2. Oxygen (O): There are 2 oxygen atoms: . Total Atomic Count. Now, we can sum all the atoms: Nitrogen (N): 2, Hydrogen (H): 8, Carbon (C): 2, Oxygen (O): 2. Total Atomicity Calculation: 14 11 / 50 11. chem_formula17_IF a molecule of an element is formed by two atoms. Then the atomicity of 3 molecules of the element will be A) three B) six C) two D) nine If each molecule has an atomicity of 2 (formed by 2 atoms), then 3 molecules will have 3×2=6 atoms. 12 / 50 12. chem_formula14_Which of the following is not correct about metallic bond A) it can occur between different elements or same element B) it gives metal their characteristics C) it is the bond between electrons and the cations in same atom or another atom D) it occurs between strong metals and weak nonmetals Metallic bonds primarily occur between metal atoms. They do not typically form between metals and nonmetals. Instead, metallic bonds involve the attraction between positively charged metal ions (cations) and a "sea of delocalized electrons." 13 / 50 13. chem_formula3_Which of the following is not correct about the atomic number and electronic configuration regarding chemical combinations A) the atomic number suggests the valency of the element B) the electronic configuration detemines the name of the element C) the atomic number suggests the group of the element D) the electronic configuration suggests whether the element is metal or non-metal The atomic number suggests the valency of the element because the atomic number indicates the number of protons and, in a neutral atom, the number of electrons. The valency is often related to the number of valence electrons, which can be inferred from the atomic number. 2. The atomic number suggests the group of the element because the atomic number helps determine the group in the periodic table. Elements in the same group have similar valence electron configurations and thus similar chemical properties. 3. The electronic configuration suggests whether the element is metal or non-metal. Explanation: This statement is generally correct. Elements with certain electronic configurations (e.g., those with fewer valence electrons, typically found in groups 1 and 2) are usually metals, while those with more valence electrons (e.g., groups 4-8) tend to be non-metals. 4. The electronic configuration does not determine the name of the element . While the electronic configuration can provide information about the element's properties and behavior, it does not determine the name of the element. The name of an element is based on its identity, which is defined by its atomic number, not its electronic structure. 14 / 50 14. chem_formula42_if the atom of a newly found element has 64 electrons , what will be the atomic number of the atom A) 64 B) 96 C) 32 D) 128 Understanding Atomic Number: The atomic number of an element is defined as the number of protons in its nucleus, which is equal to the number of electrons in a neutral atom. Given: The atom has 64 electrons. Conclusion: Therefore, the atomic number of the atom is 64 15 / 50 15. chem_formula27_which of the following is a radical A) 2Al2O3 B) O2 C) 2H2O D) NO2- A radical (or ion) is a group of atoms that carries a charge. NO₂⁻ is a nitrite ion, which has a negative charge. The other options (2Al₂O₃, O₂, 2H₂O) are neutral molecules 16 / 50 16. chem_formula48_Which of the following is correct about the Relative atomic mass of atoms A) The mass of hydrogen is assigned a basic mass of value 10. B) The relative atomic mass of an atom is the ratio of the mass of the atom compared to the mass of hydrogen and it has no unit. C) The mass of an atom that exists in isotopy is the weighted average of the mass of its isotopes. D) The relative atomic mass of oxygen is 16 and the relative atomic mass of nitrogen is 24 The mass of hydrogen is actually assigned a value of 1 (specifically, 1 atomic mass unit, or amu), not 10. The other statements are correct regarding relative atomic mass. 17 / 50 17. chem_formula41_If atom has electronic configuration of 1s2-2s2-2p3, what is the number of bonds it can form A) 5 B) 8 C) 3 D) 2 The outermost shell (n=2) has: 2 electrons in the 2s subshell. 3 electrons in the 2p subshell. Total electrons in the outer shell = 2+3=5. To achieve a stable octet (8 electrons), this atom can form bonds by either sharing or gaining electrons. Calculating Bonds: It needs 3 more electrons to complete its octet (8 total). This means it can form 3 bonds with other atoms. 18 / 50 18. chem_formula15_Which of the following is not a force of attraction between molecules in covalent bond A) van der waal force B) dipolar bond C) metallic bond D) hydrogen bond Van der Waals force:: This is a type of weak intermolecular force that arises from temporary dipoles in molecules. It is indeed a force of attraction between molecules, especially in covalent compounds. Hydrogen bond are strong intermolecular attractions that occur between molecules where hydrogen is covalently bonded to highly electronegative atoms (like oxygen, nitrogen, or fluorine). This is also a force of attraction in covalent compounds. dipolar bond typically refers to dipole-dipole interactions, which occur between polar molecules and are a type of intermolecular force. Therefore, it is a force of attraction between polar covalent molecules. Metallic bond. Metallic bonds are not forces of attraction between molecules; rather, they are a type of chemical bond that occurs between metal atoms. In metallic bonding, electrons are delocalized among a lattice of metal cations, creating a "sea of electrons." This type of bonding does not pertain to molecular attraction in covalent compounds. The metallic bond is between atoms whereas the others are between molecules. The covalent bonds occurs between atoms to form molecules then the molecules formed can now have forces of attraction between them such as van der waal, dipolar or hydrogen force 19 / 50 19. chem_formula40_If atom has electronic configuration of 1s2-2s2-2p3, what is the valency A) 3 B) 8 C) 5 D) 2 this is the number of electrons it requires to assume a stable state, or the number of bonds it can form 20 / 50 20. chem_formula18_if two atoms of B combine with one atom of A to form one molecule (AB2), what is the atomicity of AB2 A) five B) four C) three D) two The molecule AB₂ consists of 1 atom of A and 2 atoms of B, totaling 1+2=3 atoms. 21 / 50 21. chem_formula12_which of the following is not correct about covalent A) the bond dissolve in organic solvent such as ethanol and benzene B) The compound formed is insoluble in water C) it is stronger than ionic bond D) the compound formed can be gases Covalent bonds involve the sharing of electrons between atoms, and while they can be strong, ionic bonds are generally stronger due to the strong electrostatic attraction between oppositely charged ions. 22 / 50 22. chem_formula29_which of the following chemical formula is not correctly written A) Ca(OH)2 B) Fe2O3 C) Al3(SO4) D) Mg(NO3)2 The correct formula should be Al₂(SO₄)₃. The sulfate ion (SO₄²⁻) has a charge of -2, so to balance the +3 charge of aluminum (Al³⁺), we need two aluminum ions and three sulfate ions. The other formulas are correctly written. 23 / 50 23. chem_formula50_What is the empirical formula of an organic compound, which contains 80% Carbon and 20% hydrogen [C=12, H=1] A) CH3 B) C3H2 C) C2H D) C2H3 This means that in every 100g of the organic compound, the masses of carbon and hydrogen are 80g (80%) and 20g (20%) respectively. (C = 12, H = 1) for carbon 80/12= 6.6 and 20/1= 20. 6.6 is the smaller unit so 6.6/6.6= 1 and 20/6.6= 3. So the emperical formular will be CH3 24 / 50 24. chem_formula32_which of the following is correct about atomic mass of an atom X A) it is estimated relative to carbon-12 becomes atoms are usually to small to measure B) it is the mass of the atom multiplied by two C) it is the exact mass of the atom can be measured with spectrometer D) it is relative to the mass of the atom it self Atomic mass is commonly expressed in atomic mass units (amu) relative to the carbon-12 isotope, which is defined as exactly 12 amu. This method is used because atomic masses are indeed very small and difficult to measure directly 25 / 50 25. chem_formula5_An element A with electronic configuration 1s2-2s2-2p6-3s2 combines with another elememt B with electronic configuration 1s2-2s2-2p6-3s2-3p5. Which of the following is correct regarding the electronic configuration in the principal KLM shells A) A is (2,8,0) and B is (2,6,7) B) A is (2,8,5) and B is (2,8,5) C) A is (2,7,7) and B is 2,8,7) D) A is (2,8,2) and B is (2,8,7) Element A: The electronic configuration 1s2 -2s2- 2p6- 3s2 can be summarized in terms of the principal shells: K shell (n=1): 2 electrons (from 1s2-1s2). L shell (n=2): 8 electrons (from 2s2 and 2p6). M shell (n=3): 2 electrons (from 3s2). Thus, A is (2, 8, 2). For Element B: The electronic configuration 1s2 -2s2- 2p6 -3s2 -3p5 can be summarized as: K shell (n=1): 2 electrons L shell (n=2): 8 electrons. M shell (n=3): 7 electrons (2 from 3s2 and 5 from 3p5). Thus, B is (2, 8, 7) 26 / 50 26. chem_formula49_The mass of a matter tha has one-twelfth the mass of carbon-12 is A) avogadro's number B) electron mass unit C) atomic mass unit D) proton mass unit The atomic mass unit (amu) is defined as one-twelfth of the mass of a carbon-12 atom. This unit is used to express atomic and molecular masses. 27 / 50 27. chem_formula22_a molecule composed of more than 3 atoms is A) triatomic B) electrovalent C) mole D) polyatomic A polyatomic molecule contains more than three atoms. For example, sulfuric acid (H₂SO₄) is a polyatomic molecule. 28 / 50 28. chem_formula26_A group of atoms of two or more elements having a negative or positive charge is a A) anion B) triatom C) radical D) cation A radical (or ion) is a group of atoms that carries a charge. If it has a positive charge, it is called a cation; if it has a negative charge, it is called an anion. 29 / 50 29. chem_formula43_A hydrated salt of formula MSO4.xH2O CONTAINS 45.3% by mass of water of crystalisation. Calculate the value of x [M = 56, S = 32, O = 16, H = 1 ] A) 7 B) 9 C) 5 D) 3 simply put: One molecule of MS04 plus Xmolecules of H2O together make up 100peercent of the substance . And water of crystallization is 45.3 and remaining is MSO4 . so 1 molecule of MSO4 is equivalent to 54.7. now The molar mass of MSO4= M=56, S=32 , O4= 64 is 152 and molarmass of water is , XH2= 2x, XO= 16x . 18x. so MSO4 accounts for 54.7% and water of cystallization 2x + 16x account for percentage 45.3. So 152 equivalent 54.7 and 18x is equivalent to 45.3 solving for x molecules [18x=(45.3 x 152)/54.7]. x=7 or another way To find the value of x in the hydrated salt MSO4⋅xH2O with 45.3% by mass of water of crystallization, we can follow these steps: Given Data:Molar mass of M (metal) = 56 g/mol, Molar mass of sulfur (S) = 32 g/mol, Molar mass of oxygen (O) = 16 g/mol and Molar mass of hydrogen (H) = 1 g/mol. Step 1: Calculate the molar mass of MSO4. It will be qual to 152g/mol( Molar mass of MSO4=M+S+4O=56+32+4×16). Step 2: Calculate the molar mass of water (H2O), Molar mass of H2O=2H+O=2×1+16=18 g/mol. Step 3: Write the expression for the total molar mass of the hydrated salt. MSO4⋅xH2O it will be: Molar mass of MSO4⋅xH2O=152+18x . Step 4: Set up the equation using the percentage composition of water and solve for. The mass of water in the hydrated salt is 18x and the total mass of the hydrated salt is 152+18x. We know that the percentage of water is 45.3%, so we can set up the equation [18x/(152+18x)] x100=45.3 30 / 50 30. chem_formula11_which of the following is not correct about electrovalent or ionic bond A) the compound formed is soluble in organic solvents B) the compound formed is soluble in water C) the compound formed dissolves in water to form electrolytes D) the compound formed has high boiling point Ionic compounds are generally not soluble in nonpolar organic solvents. They are more soluble in polar solvents like water. This is because organic solvents typically do not have the ability to stabilize the charged ions. 31 / 50 31. chem_formula38_The emperical formula of a compound is calculated from A) the percentage composition of each element B) from the molecule of each element C) from the mole of each element D) from the number of atom of each element The empirical formula represents the simplest whole-number ratio of the elements in a compound, and it can be calculated from the percentage composition of each element. Here’s how to do it step by step:Steps to Calculate the Empirical Formula from Percentage Composition: Convert Percentage to Mass: Assume you have a 100 g sample of the compound. This means the percentage of each element can be directly treated as grams. For example, if the composition is 40% carbon and 60% oxygen, you would have 40 g of carbon and 60 g of oxygen. Convert Mass to Moles: Use the molar mass of each element to convert grams to moles:moles of element=mass of element (g)/molar mass of element (g/mol)Find the Simplest Ratio: Divide the number of moles of each element by the smallest number of moles calculated. This gives you a ratio. If necessary, multiply these ratios by a whole number to obtain whole-number values. 32 / 50 32. chem_formula20_The following elements are diatomic except A) hydrogen B) chlorine C) phosphorus D) oxygen Chlorine (Cl₂), Hydrogen (H₂), and Oxygen (O₂) are diatomic, meaning they exist as two-atom molecules. Phosphorus typically exists as P₄ or in other forms, not as a diatomic molecule. 33 / 50 33. chem_formula4_An element R with atomic number 3 and another element Q with atomic number 8 undergo a chemical reaction. Which of the following is not correct A) The electronic configuration of Q is 1s2-2s2-2p4 B) the valency of Q is -2 C) The valency of R is +1 D) the electronic configuration of R is 1s2-2p1 Element R (Atomic Number 3). Atomic Number: 3 corresponds to lithium (Li). Electron Configuration: The electron configuration for lithium is: 1s² 2s¹. The Valency: Lithium has one valence electron in the 2s orbital, so its typical valency is +1 when it loses that electron. Element Q (Atomic Number 8). Atomic Number: 8 corresponds to oxygen (O). Electron Configuration: The electron configuration for oxygen is: 1s² 2s² 2p⁴. Valency: Oxygen has six valence electrons (2 in the 2s and 4 in the 2p), and it typically gains two electrons to achieve a full outer shell, giving it a valency of -2. The electronic configuration of R written as 1s²-2p¹ is not correct. 34 / 50 34. chem_formula19_if two atoms of B combine with one atom of A to form one molecule ( AB2), what is the atomicity of 4AB2 A) four B) eight C) three D) two Each AB₂ molecule has an atomicity of 3. Therefore, for 4 molecules of AB₂, the total atomicity is 4×3=12 35 / 50 35. chem_formula23_Which of the following is not correct about how to write chemical formula A) the number of molecules is written as normal number B) the number of atoms comes after the symbol C) the number of atoms is written as superscript D) the number of molecules comes before the symbol of the atoms In chemical formulas, the number of atoms is written as a subscript (e.g., H₂O), not superscript. 36 / 50 36. chem_formula36_What is the relative atomic mass of M in M2O3 if the relative molecular formula is 160 [O=16] A) 112 B) 56 C) 48 D) 64 Molecular mass of M2O3=2×mass of M+3×mass of O. 160=2M+(3×16), 160=2M+48, 160−48=2M, 112=2M, M=112/2=56 37 / 50 37. chem_formula44_A hydrated salt of formula MSO4.xH2 O CONTAINS 37% by mass of water of crystalisation. Calculate the value of x [M = 56, S = 32, O = 16, H = 1 ] A) 8 B) 3 C) 5 D) 7 One molecule of MS04 plus Xmolecules of H2O together make up 100percent of the substance . And water of crystallization is 37 and remaining is MSO4 . so 1 molecule of MSO4 is equivalent to 54.7. now The molar mass of MSO4= M=56, S=32 , O4= 64 is 152 and molarmass of water is , XH2= 2x, XO= 16x . 18x. so MSO4 accounts for 63% and water of cystallization 2x + 16x account for percentage 37. So 152 equivalent 63 and 18x is equivalent to 45.3 solving for x molecules [18x=(37x 152)/63] x=7 38 / 50 38. chem_formula25_Which of the following is not correct about the following molecular formula 2Al2O3 (where the 2 after the Al is subscript and the 3 after the O is also subscript) A) there are four atoms of aluminium B) there are two molecules of aluminium oxide C) there are six atoms of oxygen D) the atomicity is 10 The formula 2Al₂O₃ indicates there are 2 molecules of Al₂O₃, which means there are 2×2=4 atoms of aluminum and 2×3=6 atoms of oxygen, giving a total atomicity of 10. 39 / 50 39. chem_formula6_An element A with electronic configuration 1s2-2s2-2p6-3s2 combines with another elememt B with electronic configuration 1s2-2s2-2p6-3s2-3p5. Which of the following is not correct A) B is a group 5 element element B) B is a nonmetal C) A is a metal D) A is group 2 element B is a Group 5 element:False: Element B has a configuration ending in 3p5, indicating it belongs to Group 17 (halogens), not Group 5 40 / 50 40. chem_formula34_Calculate the molecular mass of CaCO3 [ Ca=40, C=12, O=16) A) 120 B) 120mg C) 100mg D) 100 Molecular Mass of CaCO₃. Given: Ca = 40, C = 12, O = 16 (and there are 3 oxygen atoms in CaCO₃) Calculation: molecular mass of CaCO3=mass of Ca+mass of C+3×mass of OMolecular mass of CaCO3=mass of Ca+mass of C+3×mass of O =40+12+3×16, =40+12+48 =100 41 / 50 41. chem_formula33_the relative molecular mass of an atom, element or molecule is written in A) mg per Kg B) no unit C) mg per meter D) mg per volume The relative molecular mass is a ratio of the mass of a molecule to a reference mass (usually the mass of a carbon-12 atom). It is expressed as a pure number without any units. 42 / 50 42. chem_formula16_The number of atoms in one molecule of an element is called A) emperical formula B) atomic number C) mass number D) atomicity Atomicity refers to the number of atoms in a single molecule of an element. For example, diatomic elements like oxygen (O₂) have an atomicity of 2. 43 / 50 43. chem_formula8_Which of the following is not correct about covalent bond A) it occurs between element in groups 1 and 2 of the periodic table B) the two elements share electrons C) it occurs when none of the combining elements can give away their electrons D) no element donates electron completely No element donates electrons completely.This statement is correct. In a covalent bond, electrons are shared between atoms rather than one atom completely donating an electron to another. In a covalent bond, the electrons are shared. Covalent bonds occurs when when none of the combining elements can give away their electrons. And it occurs in combination between nonmetals. The elements in group 1 and 2. covalent bonds primarily occur between nonmetals, which are typically found in groups 13-18. Elements in groups 1 (alkali metals) and 2 (alkaline earth metals) tend to form ionic bonds rather than covalent bonds 44 / 50 44. chem_formula13_Which of the following is not correct about dative or coordinate covalent bond A) one element does not donate but shares in the donated electron B) one element donates the shared electron C) the characteristics as similar to covalent bond D) it is stronger than ionic bond Dative (coordinate) bonds can vary in strength, but ionic bonds are typically stronger than covalent bonds (including dative bonds) due to the strong electrostatic attractions between oppositely charged ions. 45 / 50 45. chem_formula35_Calculate the molecular mass of Mg(NO3)2 [ Mg=24, N=14, O=16) A) 160 B) 148 C) 138 D) 152 Molecular mass of Mg(NO3)2=mass of Mg+2×mass of N+6×mass of O. =24+(2×14)+(6×16). =24+28+96. =148 46 / 50 46. chem_formula10_Which of the following is not correct about ionic or electrovalent bond A) in the molten state the ions are not charged B) the compound formed is not charged C) the compound formed has high melting point D) the compound formed is a solid Ionic bonds form between metals and nonmetals, resulting in neutral solid. Because the negative and positive charges from the combining ions cancel out and all the electrons are in bound state, there will be no free electrons. The compound formed is a solid: This is correct. Ionic compounds typically form crystalline solids at room temperature. The compound formed has a high melting point: This is also correct. Ionic compounds generally have high melting and boiling points due to strong electrostatic forces between the oppositely charged ions. In the molten state, the ions are released from their bound state and the molten state becomes charged and can conduct electricity. 47 / 50 47. chem_formula28_which of the following will be produced from the combination of Ca2+ and OH- A) Ca2OH B) Ca(OH)2 C) CaOH2 D) CaO2H2 When calcium ions (Ca²⁺) combine with hydroxide ions (OH⁻), the resulting compound is calcium hydroxide, represented as Ca(OH)₂. This formula reflects that there are two hydroxide ions for each calcium ion. 48 / 50 48. chem_formula7_An element A with electronic configuration 1s2-2s2-2p6-3s2 combines with another elememt B with electronic configuration 1s2-2s2-2p6-3s2-3p5. What is the compound formed A) AB B) A2B C) AB5 D) AB2 Element A (Group 2, valency = 2): Tends to lose 2 electrons to form A2+. Element B (Group 17, valency = 1): Tends to gain 1 electron to form B−. To form a neutral compound: We need 2 atoms of B to balance the charge of 1 atom of A: A2+ + 2B−=AB2 49 / 50 49. chem_formula2_An element R with atomic number 3 and another element Q with atomic number 8 undergo a chemical reaction. Which of the following is correct chemical formula of the compound formed A) Q2R B) R3Q C) Q3R D) R2Q Step 1: Determine the Position and General Characteristics. Element R (Atomic Number 3): The atomic number indicates the number of protons, which also corresponds to the number of electrons in a neutral atom. Elements with atomic numbers 1, 2, and 3 are typically found on the left side of the periodic table, where metals are located. Thus, R is likely a metal. Element Q (Atomic Number 8): The atomic number 8 indicates that this element is more likely to be a nonmetal, often found on the right side of the periodic table. Step 2: Determine Valencies Valency of R (Atomic Number 3): As a metal, R most likely has a valency of +1 (common for Group 1 metals). Valency of Q (Atomic Number 8): As a nonmetal, Q likely has a valency of -2 (common for elements in Group 16, which require two additional electrons to achieve a full outer shell). Step 3: Balancing Charges To form a stable compound, the total positive charge from R must balance the total negative charge from Q. Since R has a valency of +1 and Q has a valency of -2: To balance the charges, we need two atoms of R to provide a total of +2 charge to balance the -2 charge from one atom of Q. Step 4: Determine the Chemical Formula From the analysis: 2 atoms of R: R2. Thus, the correct formula for the compound formed is: R2Q 50 / 50 50. chem_formula21_A molecule composed of 3 atoms is A) triatomic B) polyatomic C) monoatomic D) diatomic A triatomic molecule consists of three atoms. For example, ozone (O₃) is a triatomic molecule. 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 Biology: Transportation Vol 2Next PostBiology: Sense Organ
