Chemistry

Sedimentation is the process where suspended solid particles settle out of a fluid under the influence of gravity.

A compound is a substance formed from two or more elements that are chemically bonded together in fixed ratios, unlike mixtures where the components retain their individual properties

Silicon is the second most abundant element in the Earth’s crust, primarily found in silicate minerals

Water is not considered an organic solvent; it is a polar solvent. Organic solvents include substances like propanone, alcohol, and turpentine.

In a tincture of iodine, iodine is the solute that is dissolved in alcohol (the solvent). The tincture is a solution used as an antiseptic

Liquids take the shape of their container. Solids maintain their shape, while gases expand to fill the entire volume of the container.

Chemistry is the scientific discipline that studies the properties, composition, and changes of matter, including how substances interact and react with each other

Sand is primarily composed of silicon dioxide (SiO₂), which consists of silicon and oxygen.

A compound is a pure substance formed from two or more elements combined in fixed ratios, not just any combination of substances

An emulsion is a mixture of two immiscible liquids where one is dispersed in the other

Elements are generally classified into metals and nonmetals based on their physical and chemical properties.

Oxygen is a gas and not an organic solvent. Propanone and benzene are examples of organic solvents, while turpentine is also organic.

Metals are excellent conductors of heat and electricity. This characteristic is crucial for their use in electrical applications

Silicon and oxygen are the most abundant elements in the Earth’s crust, primarily found in silicate minerals.

Brine is a solution, not a colloid. Honey, glue, and milk are colloidal solutions.

In a solution, the solvent typically makes up the greater volume compared to the solute

Liquids take the shape of their container and have a definite volume. They are fluid at room temperature and are not easily compressed compared to gases

Diffusion is the process where particles move from an area of higher concentration to an area of lower concentration until equilibrium is reached. The statement is incorrect because it describes the opposite of how diffusion works

Silicon is a well-known metalloid, exhibiting properties of both metals and non-metals. Gold, carbon, and silver are not metalloids

Evaporation is the process where molecules at the surface of a liquid gain enough energy to transition into the gas phase at temperatures below the boiling point.

In osmosis, the solvent (usually water) moves from an area of lower solute concentration to an area of higher solute concentration through a semipermeable membrane. The solute itself does not move in osmosis.

Water is indeed immiscible with oil, as oil and water do not mix due to their differing polarities. The other statements about water being a universal solvent, polar, and dissolving organic solutes are true

Compounds are generally classified into organic (containing carbon) and inorganic (typically lacking carbon)

Most metals have high melting points. While some non-metals can have low melting points, metals are usually solid at room temperature with higher melting points

Solids have a definite shape and volume and are generally not compressible. The particles in solids are closely packed and have fixed positions

Matter is anything that has mass and occupies space. It is the substance that makes up all physical objects in the universe.

Steel is an alloy primarily made of iron, with carbon as the solute. The carbon is dissolved in iron to improve its strength and hardness

Oxygen and silicon are the most abundant element in the Earth’s crust and is essential for life.

Matter is anything that has mass and occupies space. It is the substance that makes up all physical objects in the universe.

An element is a fundamental substance that cannot be decomposed into simpler substances through chemical reactions. Atoms and ions are components or forms of elements, but they are not standalone substances

Non-metals are generally brittle and cannot be easily shaped, unlike metals which can be stretched and drawn. However, some non-metals can exist in forms that can be molded.

A saturated solution contains the maximum amount of solute that can dissolve at a given temperature.

The Tyndall effect describes the scattering of light by particles in a colloid, making the path of the light visible.

Mixtures do not have fixed proportions; the components can vary in amount

Gas particles are in constant motion and have no fixed positions. They occupy all available space in a container, unlike solids and liquids

A diluted solution contains a small amount of solute compared to solvent.

A chemical change results in the formation of new substances with different properties. This change is generally irreversible (e.g., burning wood).

Compounds can be represented by chemical formulas, while mixtures cannot, as they do not have a consistent composition.

Brine is a saturated solution of salt (sodium chloride) in water

An aerosol is a mixture where tiny liquid or solid particles are dispersed in a gas.

Metals are generally malleable (can be hammered into shape) and ductile (can be drawn into wires). Brittleness is typically a property of non-metals

A concentrated solution has a high amount of solute relative to the amount of solvent

The three primary states of matter are solid, liquid, and gas. “Dense” is not a state of matter.

An atom is the smallest unit of an element that retains the chemical properties of that element. Ions are charged particles derived from atoms, and delimiters are not relevant to this context

A physical change involves alterations in the state or appearance of a substance without changing its chemical composition (e.g., melting ice). The change can be reversed

Metalloids exhibit properties of both metals and non-metals. They can have metallic luster but are brittle and poor conductors compared to metals.

Non-metals generally have low densities compared to metals. Most non-metals are gases at room temperature, and those that are solid (like sulfur and phosphorus) are also less dense than metals

Brass is an alloy primarily made of copper and zinc. In the context of alloys, the main component (in this case, copper) is considered the solvent, while the other metal (zinc) acts as the solute

A gel is a colloidal system where a solid is dispersed in a liquid, giving it a jelly-like consistency

A pure substance consists of only one type of particle and has a uniform composition. Impure substances contain multiple components

Molecular number is not a property typically used in the physical separation of mixtures. Properties like weight, solubility, and melting point are commonly used

Chromatography separates components of a mixture based on their different affinities to a stationary phase and a mobile phase, making it effective for colored substances.

Crystallization is a method used to separate a soluble solid from a solution by forming solid crystals, typically by evaporating the solvent.

In an aqueous mixture of sodium chloride (salt) and sand, sand is insoluble in water. When you perform filtration, the sand (solid) will remain on the filter paper, while the sodium chloride (dissolved in water) will pass through as part of the filtrate. Afterward, you can obtain pure sodium chloride by evaporating the water from the filtrate.

Sublimation is a method that can separate solids based on their ability to transition directly from solid to gas. For example, separating iodine from salt.

This is a chemical change known as slaking, where quicklime (calcium oxide) reacts with water to form calcium hydroxide, resulting in a new substance.

Distillation is effective for separating ethanol and water due to their different boiling points.

Crystallization is specifically used to separate solids from solutions, not for separating solid mixtures directly.

When warm air meets the cold surface of the bottle, water vapor condenses into droplets.

Distillation is primarily used for separating liquids based on boiling points, not for separating solids.

Dissolving salt in water is a physical change, as no new substances are formed; the salt can be recovered by evaporation.

Hand-picking: This method relies on the physical appearance (color, size) of the components to separate them manually.Centrifugation: This technique separates components based on their mass and density by spinning them at high speeds.Distillation: This method separates substances based on differences in their boiling points, not their color or mass.Filtration: This technique separates solids from liquids or gases based on particle size.

Explanation: Ammonium chloride undergoes sublimation when heated, converting directly from solid to gas without becoming liquid. The white deposit observed is likely the result of gas cooling and solidifying.

burn is a chemical reaction in which a substance combines with oxygen, often resulting in a change in the chemical composition and the formation of a new substance.

Sublimation is the process where a solid transitions directly to gas without becoming liquid.

Boiling Point: Nitrogen and oxygen are separated from air through a process called fractional distillation. This method takes advantage of the different boiling points of these gases. Nitrogen has a boiling point of approximately -196°C, while oxygen has a boiling point of approximately -183°C. By cooling air and then distilling it, these gases can be effectively separated.

Centrifugation is a technique that uses rapid spinning to separate components of blood based on their density. Blood cells settle at the bottom, while plasma remains on top

Fractional distillation separates liquid mixtures based on differences in boiling points and densities.

Crystallization allows for the recovery of solid solutes from a solution while leaving the solvent intact.

the molecule is the smallest particle of a compound which is capable of independent existence. An atom is the smallest unit of a compound capable of taking part in a chemical reaction

Gravity is a force and not a separation method itself. Seiving, centrifugation, and chromatography can involve separation based on particle size.

Chromatography relies on the different adsorption properties of substances to separate them as they move through a medium

Mercury is a pure substance, while the others are mixtures of various components.

Residue refers to what is left behind after a process, whereas ion, atom, and molecule are all fundamental constituents of matter.

Bronze is an alloy a mixture of copper which is the solvent and tin which is the solute. Ie tin dissolved in copper. Bronze typically consists of about 90% copper and 10% tin,The addition of tin to copper improves the strength, corrosion resistance, and overall durability of the metal, making bronze suitable for various applications, including tools, weapons, and sculptures though the proportions can vary.

Distillation separates components of a mixture based on differences in boiling points, not particle size. Other methods like sifting, filtration, and centrifugation can involve particle size.

Centrifugation uses centrifugal force to separate solids from liquids in a colloidal suspension by causing the solid particles to settle at the bottom.

Distillation is the best method to separate water from a sugar solution, as it uses differences in boiling points to evaporate the water, leaving the sugar behind.

Fractional distillation separates petroleum into its various components based on boiling points

Dissolution: Refers to the process of a substance dissolving in a solvent, not a separation method

This statement is incorrect. An ion is formed when an atom gains or loses electrons, but the number of electrons gained or lost is equal to the ion’s charge, which corresponds to its valency, not twice its valency

A compound is a pure substance formed when two or more elements chemically combine in fixed proportions, resulting in new chemical properties.

Distillation separates liquids based on their boiling points. It is commonly used to purify liquids or separate liquid mixtures.

A chemical equation describes a chemical reaction rather than a physical property used for separation. Properties like color, size, and density are often used to separate mixtures.

Sugar dissolves in water while sulfur does not. The mixture can be filtered to remove sulfur, and the sugar solution can then be evaporated to recover sugar.

A separating funnel is ideal for separating immiscible liquids like kerosene (a hydrocarbon) and water.

Blood is a mixture because it contains various components, including red blood cells, white blood cells, platelets, and plasma, which are not chemically bonded and retain their individual properties. Sand is also a mixture, but the question specifies “an example,” so blood is a more complex example.

Fractional distillation is used to separate mixtures of liquids with different boiling points, such as the various components of petroleum.

Freezing ice-cream is a physical change because it involves a change in the state of matter from liquid to solid without altering the chemical composition of the ingredients. The ice-cream can be melted back to its original state.

Distillation is used for separating components of a liquid mixture, not specifically for recovering solids from liquids.

Vaporisation occurs when a liquid turns into a gas at its boiling point. This includes both boiling and evaporation, but at the boiling point, it specifically refers to the rapid conversion to gas.

Kerosene is a hydrocarbon fuel that does not contain oxygen in its composition.

This reaction involves combustion, which is a chemical change that results in the formation of new substances (ash, gases) from the original materials (wood)

A separating funnel is specifically designed to separate two immiscible liquids based on their different densities.

Fractional crystallization separates solids based on their different solubilities in a solvent, allowing for the recovery of multiple solids.

The change in color of zinc oxide with heating and cooling is a physical change, as it does not involve a change in the chemical composition of the substance

Chromatography is a technique used to separate components of a mixture based on differences in their movement through a medium. It is effective for separating liquids.

Entropy is a measure of disorder or randomness in a system. As temperature increases, particles move more rapidly and the disorder in the system increases.

This statement is incorrect because physical changes do not produce new substances; they only change the state or appearance of a substance. Chemical changes result in new substances being formed.

Isotope A: Has a mass of 10 and a relative abundance of 70% (0.70). Isotope B: Has a mass of 11 and a relative abundance of 30% (0.30). Contribution of A=Mass of A×Relative abundance of A=10×0.70=7.0. Contribution of B=Mass of B×Relative abundance of B=11×0.30=3.3. adding the two gives 10.3

The d-subshell has five orbitals, which can hold a maximum of 10 electrons.

To find the relative atomic mass of the element with isotopes X-23 and X-24 existing in a ratio of 3:1, we can follow these steps:Step-by-Step Calculation: Isotope1 X-23 has a mass1 of 23 and exists in a ratio of 3. And Isotope2 X-24 has a mass2 of 24 and exists in a ratio2 which is 1. Calculate the weighted average:The relative atomic mass AA can be calculated using the formula: A=(mass1×ratio1)+(mass2×ratio2)/(ratio1+ratio2)=(23×3)+(24×1)/3+1=23.25

An atom is electrically neutral when it has the same number of positively charged protons in the nucleus as negatively charged electrons surrounding the nucleus. This balance results in no overall charge.

The mass of an electron is very small compared to that of protons and neutrons, so it does not significantly contribute to the overall mass of the atom.

The maximum number of electrons in a shell can be calculated using 2n raised to power 2 or n-squared. For the 4th shell (n=4n=4): 2(4-squared)=2(16)=32

Each orbital can hold a maximum of 2 electrons due to the Pauli exclusion principle.

The number of neutrons can be calculated using the formula: Neutrons=Mass Number−Atomic NumberNeutrons=Mass Number−Atomic Number For this atom, it would be: 40−21=1940−21=19

one molecule of Cl is monoatomic, one molecule of oxygen (O2) is diatomic, if the element contains 3 atoms it is triatomic eg , Ozone , O3 if the molecule of the element contains 4

Protons have a positive charge, while electrons carry a negative charge. This statement is incorrect.

In a neutral atom, the number of electrons equals the number of protons, which is the atomic number. Here, the atomic number is 8, so there are 8 electrons.

The relative atomic mass of nitrogen is approximately 14.01, not 36. The other values are correct: carbon is 12, hydrogen is 1, and oxygen is 16.

A mass spectrometer separates particles based on their mass-to-charge ratio. If an element shows two peaks in the mass spectrum, it means that there are two different masses present, which corresponds to the presence of two isotopes of that element. Isotopes are atoms of the same element that have different numbers of neutrons, resulting in different atomic masses

These are the three fundamental subatomic particles that make up an atom. Protons are positively charged, neutrons are neutral, and electrons are negatively charged.

they are atoms of same elements with the same atomic number (Z) but different mass number. This means they have the same number of protons but different number of neutrons in their nucleus

The mass of an atom is actually estimated relative to carbon-12 (¹²C), not oxygen-16 (¹⁶O). The atomic mass unit (amu) is defined based on the mass of carbon-12, where 1 amu is a twelfth of the mass of a carbon-12 atom.

The electron configuration for 12 electrons is 1s2, 2s2, 2p6, 3s2, meaning the last electron is in the third shell.( the first shell has 2 electrons, the second shell holds 8 electrons and the remaining 2 go into the third shell

In a neutral atom, the number of electrons equals the number of protons, which is the atomic number. Here, the atomic number is 21, so there are 21 electrons.

The f subshell has 7 orbitals, and since each orbital can hold 2 electrons, it can hold a total of 7×2=147×2=14 electrons.

The L shell can hold a maximum of 8 electrons. The total number of electrons in a shell can be calculated using the formula 2n22n2, where nn is the shell number (for L, n=2n=2).

Atoms with a fully filled valence shell typically resemble noble gases and are chemically inert (non-reactive). This configuration is stable and is often referred to as the noble gas configuration.

To find the relative atomic mass of the element with isotopes X-20 and X-22 existing in a ratio of 3:1, we can use the following calculation:Step-by-Step Calculation:Identify the isotopes and their ratios: Isotope1 X-20 has a mass1 of 20 and exists in a ratio1= 3. Isotope2 X-22 has a mass2 of 22 and exists in a ratio2 of 1. Calculate the weighted average:The relative atomic mass formula: =(mass1×ratio1)+(mass2×ratio2)/(ratio1+ratio2). So if we plug the values into the formula: A=(20×3)+(22×1)/(3+1)= 22.5

Valence electrons are the electrons in the highest energy level (outermost shell) of an atom and are involved in chemical bonding.

The first electron fills the 1s orbital in the first shell.

Protons carry a positive charge. The statement about protons being neutral is incorrect.

Electrons occupy the shells (energy levels) around the nucleus of an atom. Protons and neutrons are found in the nucleus.

The mass number is the sum of the number of protons and neutrons in an atom’s nucleus. It does not include electrons.

An orbital is a region in an atom where there is a high probability of finding electrons

The configuration is written some thing like 1s2-2s2-2p6. the first number is the shell number which is first written as whole number starting from 1 for K, 2 for L , 3 for M etc. then it is followed by the subshell which  is s, p,d or f and then the number of electrons in the subshell orbit is written last as superscript. so the 6 in 1p6 is the number of electrons

Dalton’s atomic theory states that atoms combine in whole-number ratios to form compounds. The statement about combining in “small fractions” contradicts this principle.

In the quantum mechanical model, electrons do not move in fixed circular paths. Instead, they exist in probabilistic orbitals around the nucleus.

The mass number can be calculated using the formula: Mass Number=Atomic Number+NeutronsMass Number=Atomic Number+Neutrons For this atom, it would be: 8+7=158+7=15

The d subshell has 5 orbitals, and since each orbital can hold 2 electrons, it can hold a total of 5×2=105×2=10 electrons.

An atom is composed of a nucleus (containing protons and neutrons) and electron shells (where electrons reside). The other options do not correctly represent the structure of an atom.

Neon (atomic number 10) has a complete outer shell with 8 valence electrons, which is the maximum for the outermost shell in the second period. Oxygen (8) has 6, phosphorus (15) has 5, and potassium (19) has 1 in its outermost shell.

The p-subshell has three orbitals (px, py, pz), which can collectively hold a maximum of 6 electrons.

The Aufbau principle states that electrons fill orbitals starting from the lowest energy level to the highest.

The correct notation places the shell number before the subshell letter (e.g., 2s2s, 3p3p). The other statements are accurate in their descriptions.

Key Definitions:Atomic Number (Z): The number of protons in an atom, which also determines the element’s identity. Mass Number (A): The total number of protons and neutrons in the nucleus of an atom. Neutrons: Calculated as the mass number minus the atomic number (A – Z). Electrons: In a neutral atom, the number of electrons equals the number of protons. Given: Mass Number (A) = 27 and Atomic Number (Z) = 17. Calculations: Number of Protons: This is equal to the atomic number..Protons = 17. Number of Neutrons: This is calculated as follows: Neutrons = Mass Number – Atomic Number = 27 – 17 = 10 Number of Electrons: In a neutral atom, the number of electrons equals the number of protons. Electrons = 17

A mass spectrometer is an instrument used to measure the mass-to-charge ratio of ions. It can accurately determine the atomic mass of an atom by analyzing the isotopes present. The other options (electrometer, hydrometer, thermometer) are not used for measuring atomic mass.

To find the relative atomic mass of the element with isotopes X-16, X-17, and X-18 existing in a ratio of 3:1:1, we can use the following calculation: Step-by-Step Calculation:Identify the isotopes and their ratios:Isotope1 X-16 has a mass1 of 16 and exists in a ratio1 which is3. Then Isotope2 X-17 has a mass2 of 17 and exists in a ratio2 which is 1. Finally Isotope3 X-18 has a mass3 of 18 and exists in a ratio3 with is 1. Calculate the weighted average:The relative atomic mass =(mass1×ratio1)+(mass2×ratio2)+(mass3×ratio3)/(ratio1+ratio2+ratio3). Plugging the values into the forula: =(16×3)+(17×1)+(18×1)/(3+1+1)=16.6

The s-subshell has one orbital, which can hold a maximum of 2 electrons.

Hydrogen typically has one proton and one electron, but it usually has no neutrons in its most abundant isotope (protium). There are isotopes of hydrogen that contain neutrons (like deuterium and tritium), but the most common form of hydrogen (protium) does not have any neutrons.

filling the orbitals according to the energy level. Follow the order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

The nucleus of an atom is made up of protons and neutrons. Electrons are not part of the nucleus; they orbit around it.

Dalton’s atomic theory posits that atoms are indivisible and cannot be created or destroyed in chemical reactions. This statement contradicts that principle, as atoms can only rearrange during reactions but cannot be created from other atoms.

The atomic mass scale is based on the carbon-12 isotope, which is commonly used as the standard reference for atomic masses. However, if you are specifically choosing from the options provided, the most direct answer is “carbon.”

Atomic Number: The atomic number of an element is defined as the number of protons in the nucleus of an atom and is always a whole number. It cannot be in fractions.

The f-subshell has seven orbitals, which can hold a maximum of 14 electrons.

The atomic mass unit (amu) is defined relative to carbon-12, where one amu is one-twelfth of the mass of a carbon-12 atom. This isotope serves as the standard reference point for measuring and comparing the masses of all other atoms.

The discovery of the atom is closely associated with the cathode ray experiment conducted by J.J. Thomson. In this experiment, Thomson demonstrated that cathode rays were composed of negatively charged particles (later named electrons), leading to the understanding of atomic structure.

This statement is incorrect because the s sublevel has 1 orbital (which can hold 2 electrons). The p sublevel has 3 orbitals, the d sublevel has 5 orbitals, and the f sublevel has 7 orbitals.

The correct conclusion is that cathode rays are negatively charged because they are attracted to the positive plate of the electric field. This indicates that the rays consist of negatively charged particles (electrons).

Dalton did not discover the neutron; he proposed the atomic theory that included the existence of atoms but did not identify subatomic particles like neutrons.

The atom lost an electron, so it would become Na+Na+ (a cation), not N−N− (an anion)

The heating of metal foils indicates that cathode rays transfer energy when they collide with the metal. This energy transfer is a result of the kinetic energy of the particles in the cathode rays, which are electrons. While the statement “cathode rays conduct electricity” is somewhat indirect, it reflects the fact that these rays can transfer energy and interact with matter, demonstrating their energetic properties. Note: Cathode rays are composed of electrons, not neutrons or protons, and they do travel in straight lines unless deflected by an external force.

Let’s analyze the reaction between sodium ions (Na+) and chloride ions (Cl−) to determine which statement is not correct: Statements Analysis. The empirical formula is 2NaCl: Not Correct: The empirical formula for the ionic compound formed by sodium ions and chloride ions is simply NaCl. The ratio of sodium to chloride in the compound is 1:1, not 2:1. Sodium is the cation: Correct: Sodium ions (Na+) are positively charged, making sodium the cation. Chlorine is the anion: Correct: Chloride ions (Cl−) are negatively charged, making chlorine the anion. Sodium lost one electron to chlorine: Correct: Sodium loses one electron to form Na+, and chlorine gains that electron to form Cl−

The deflection of cathode rays in an electric or magnetic field demonstrates that they are charged particles. This is fundamental to understanding their nature as electrons.

Atomic Number (Z): This represents the number of protons in the nucleus of an atom, which also equals the number of electrons in a neutral atom. The arrangement of these electrons, especially in the outermost shell (valence electrons), determines how an element reacts chemically

An atom with an atomic number of 10 is Neon (Ne). The electron configuration for Neon is. 1s2-2s2-2p6. This means Neon has 2 electrons in the 1s orbital, 2 electrons in the 2s orbital and 6 electrons in the 2p orbitals (2px, 2py, 2pz). According to Hund’s rule and the Pauli exclusion principle, the electrons will fill the 2p orbitals as follows. The first three electrons will occupy the 2px, 2py, and 2pz orbitals with upward spins. The next three electrons will pair with the first three, having downward spins. Therefore, the last electron (the 10th electron) will have a downward spin in the 2pz orbital

The K shell corresponds to the principal quantum number n = 1. The value of n for the K shell is not 3; it is the first energy level.

When an atom receives an electron, it becomes negatively charged and is referred to as an anion, not a cation. A cation is formed when an atom loses an electron.

The isotopes contribute fractions that make up the mean atomic mass. To find the percentage composition of the isotope of chlorine with a mass number of 35, we can use the formula for the weighted average of the isotopes. Let’s denote: x: the fraction of the isotope with mass 35. 1−x: the fraction of the isotope with mass 37. Mean atomic mass =35.5. So (35x)+ [(1-x)37]= 35.5. and 35x+ [37-37x]=35.5 and 35x-37x+37= 35.5 and 37-2x=35.5 . When we re arrange 2x=1.5 then X=1.5/2=0.75

The valency of an element is the number of hydrogen atoms that can combine with or replace one atom of the element. Valency of an element is also called the combining power of the element or the oxidation number of the element. It is the number of electrons in the outermost orbit of an atom Some elements have more than one valency and they are said to have variable valences

The ability of cathode rays to cause small wheels to rotate indicates that these rays possess both mass and momentum, allowing them to exert force on the wheels.

The atom that gains the electron is commonly the metal.Explanation: This statement is incorrect because the atom that gains electrons is usually a nonmetal, which becomes negatively charged and forms an anion.

The 3d orbitals are actually at a higher energy level than the 4s orbital. When filling orbitals, the 4s orbital is filled before the 3d orbitals because it has a lower energy level

The azimuthal quantum number (l) determines the shape of the orbital and describes the subshells (s, p, d, and f). The magnetic quantum number (m) describes the orientation of the orbitals within those subshells.