June 2023
5 Which statement describes a chemical property of iron? (1) Iron is malleable. (2) Iron conducts electricity. (3) Iron reacts with nitric acid.
(4) Iron has a high melting point.
Solution: A chemical property describes something that changes the identity of a substance. A chemical change represents a reaction. We are looking for a reaction here which is in choice 3. The rest of the properties described are physical properties.
Answer: 3
6 Diamond and graphite are two forms of solid carbon. These two forms of carbon have (1) different crystal structures and different properties (2) different crystal structures and the same properties (3) the same crystal structure and different properties (4) the same crystal structure and the same properties
Solution: Diamond and graphite have different structures and different properties. For example, diamond is really hard and graphite is soft.
Answer:1
7 Which substance can be broken down by a chemical change? (1) cobalt
(2) ethane (3) krypton
(4) manganese
Solution: Compounds can be broken down by a chemical change. Elements can not be broken down by a chemical change. Cobalt, krypton and manganese are elements and can be found on the Periodic Table (their names can be found in Table S). We can eliminate choices 1,3 and 4.
Answer:2
16 The melting of an ice cube is an example of an (1) endothermic, chemical change
(2) endothermic, physical change
(3) exothermic, chemical change
(4) exothermic, physical change
Solution: Chemical changes change the identity of the substance and physical changes do not. Phases changes such as melting are physical changes, eliminating choices 1 and 3. Heat is required to melt ice (go from solid to liquid). Endothermic is a process where heat is absorbed.
Answer:2
40 Which particle diagram represents a sample of xenon at STP?
Solution:Xenon is not a diatomic element, eliminating choices 3 and 4. It is in group 18 which is a Noble Gases group and would therefore be a gas. Gases are spread out and take the shape of the container.
Answer:1
PS: To memorize diatomic elements, we can use the mnemonic BrINCl HOF
January 2023
8 Which substance contains elements chemically combined in a fixed proportion?
(1) manganese
(2) methane
(3) silicon
(4) strontium
Solution: Compound is a substance that contains elements chemically combined in a fixed proportion. Manganese, silicon and strontium are all elements (can be found on the Periodic Table). Methane is the only compound and is therefore the correct answer 2.
Answer:2
13 Which substance can not be broken down by a chemical change?
(1) ammonia
(2) ethanol
(3) krypton
(4) water
Solution: Elements can not be broken down by a chemical change. Krypton is an element (you can find it on the Periodic Table) and the rest of the answer choices are compounds.
Answer:3
14 Which sample of matter is a mixture?
(1) CO2 (g)
(2) CCl4(l)
(3) MgCl2 (aq)
(4) Sn(s)
Solution: A mixture is composed of two or more substances (elements or compounds). Aq stands for aqueous which means dissolved in water. MgCl2 (aq) is a mixture because it is composed of MgCl2 and H2O. Any substance dissolved in water is a homogeneous mixture.
Answer:3
45. Which particle diagram represents one substance, only?
Solution: Elements and compounds are pure substances. When two or more of these are mixed, mixtures are created. Choice 1 represents one pure substance only because it shows atoms of one element only.
Solution: 1
August 2022
8. Hydrogen sulfide, H2S, is classified as a
(1) compound with atoms in a fixed proportion
(2) compound with atoms in a proportion that can vary
(3) mixture with atoms in a fixed proportion
(4) mixture with atoms in a proportion that can vary
Solution: H2S consists of two elements (hydrogen and sulfur) and is a compound. Compounds consist of two or more elements combined together in a fixed proportion.
Answer: 1
9. A structural formula differs from a molecular formula in that a structural formula shows the
(1) arrangement of atoms
(2) number of atoms
(3) ratio of atoms
(4) types of atoms
Solution: A molecular formula such as C2H4 simply states the number of atoms of each element present in the molecule. You can also see what types of atoms are present (carbon and hydrogen in the example shown above) and their ratio (2 to 4 in C2H4 for example) . A structural formula, on the other hand, shows the structure of the molecule and which atoms are bonded to which atoms. Arrangement of atoms should be the correct answer.
Answer: 1
14. Which sample of matter can be separated into two different substances by physical means?
(1) liquid bromine
(2) gaseous propane
(3) solid sodium acetate
(4) aqueous magnesium sulfate
Solution: Physical means separate components of a mixture while chemical means can separate compounds. We must be looking for a mixture then since physical means were used. A mixture consists of two or more different substances. Let's look through the answer choices. Liquid bromine is one element and not a mixture. Gaseous propane is a compound that consists of carbon and hydrogen. Sodium acetate is a compound as well (metal + polyatomic ion). Aqueous magnesium sulfate is a mixture. Why? Aqueous means dissolved in water. Magnesium sulfate is a compound. Therefore, we have two substances: water and magnesium sulfate. Hint: If you ever see aqueous something, it will always be a mixture!
Answer: 4
38 Given the diagram representing a classification of matter:
Which types of matter are represented by X and Z in the diagram?
(1) X is mixture, and Z is substance.
(2) X is substance, and Z is mixture.
(3) X is element, and Z is compound.
(4) X is compound, and Z is element.
Solution: A pure substance consists of one element or one compound while a mixture consists of two or more elements or compounds. Elements can be found on the periodic table. We can see that Fe is an element and should belong to the substance category. CaCO3 is a compound (two or more elements in fixed proportions) and should be under the substance category as well. Air, on the other hand, consists of different substances : oxygen, carbon dioxide, nitrogen and many more and should belong to the mixtures category. NaCl(aq) is sodium chloride dissolved in water and represents a mixture as well (two substances: sodium chloride and water).
Answer: 2
41 Which two particle diagrams represent two different phases of the same compound, only?
(1) A and B
(2) A and C
(3) B and C
(4) B and D
Solution: In a solid phase, the atoms or molecules are really close to one another with a fixed volume and shape. In a liquid phase, they are more spread out with a fixed volume but not fixed shaped. In a gas they are most spread out and don't have fixed volume or shape. The white circle represents an atom of one element and the black circle represents atom of a different element. We are asked to identify two different phases of the same compound. Choice A has two different compounds, one which two white circled and another with one white and white black. We can eliminate it. Choice C, likewise has two different compounds and can be eliminated. Choice B and D have one compound each (one black circle with one white circle). Choice D represents a solid phase since all the molecules are next to each other. Choice B represents a gaseous phase most likely since all the molecules are very spread out.
Answer: 4
June 2022
10 All matter can be classified as
(1) an element
(2) a compound
(3) a mixture or an element
(4) a mixture or a substance
Solution: All matter can be classified as a mixture or a substance. Elements and compounds fall under the substance category.
Answer: 4
11 Which sample at STP has the same chemical properties as 10. grams of Al(s) at STP?
(1) 10. grams of Si(s)
(2) 10. grams of Na(s)
(3) 5 grams of Al(s)
(4) 5 grams of Mg(s)
Solution: This question is asking about the same chemical properties. STP and the number of grams are included to distract us and are not relevant to the question. Which element would have the same chemical properties as aluminum? Same element: aluminum
Answer: 3
12 Which sample of matter can not be broken down by a chemical change?
(1) antimony
(2) ethanol
(3) methane
(4) water
Solution: Elements can not be broken down by a chemical change. Now, all we have to do is to figure out which of the answer choices is an element. This can be done by looking at the Periodic Table.
Answer: 1
13 Based on Table F, which 10.-gram sample, when thoroughly mixed with 1 liter of water at room temperature, forms a heterogeneous mixture?
(1) ammonium chloride, NH4Cl
(2) potassium iodide, KI
(3) silver bromide, AgBr
(4) sodium nitrate, NaNO3
Solution: Table F on the Reference Table is a solubility table. A compound that is soluble will dissolve in water forming homogeneous mixture. A compound that is insoluble will not be able to dissolve in water and a heterogeneous mixture will be formed. Therefore, we are looking for something that is insoluble. If we look at AgBr, we see that Br- is soluble UNLESS it is combined with Ag^+, Pb^2+, or Hg2^2+
Answer: 3
January 2020
11 Which substance can not be broken down by chemical means? (1) aluminum (2) ammonia (3) aluminum oxide (4) ammonium chloride
Solution: Elements can not be broken down by chemical means. The name of all of the elements can be found in Table S on the Reference Table.
Answer:1
August 2019
9 Which term represents the fixed proportion of elements in a compound?
(1) atomic mass
(2) molar mass (3) chemical formula
(4) density formula
Solution: Chemical formula represents the fixed proportion of elements in a compound.
Answer:1
37 Which particle diagram represents a sample of oxygen gas at STP?
Solution: Oxygen is diatomic (a molecule of oxygen has two oxygen atoms), eliminating choices 1 and 2. It is a gas as stated in the question. Gases are spread out and take the shape of the container.
Answer:4
PS: To memorize diatomic elements, we can use the mnemonic BrINCl HOF
June 2019
9 Which statement explains why NaBr is classified as a compound?
(1) Na and Br are chemically combined in a fixed proportion.
(2) Na and Br are both nonmetals.
(3) NaBr is a solid at 298 K and standard pressure.
(4) NaBr dissolves in H2O at 298 K.
Solution: Compounds have atoms of elements in fixed proportions.
Answer: Choice 1
13 Which substance can not be broken down by a chemical change?
(1) ammonia
(2) magnesium
(3) methane
(4) water
Solution: Elements can not be broken down by a chemical change. Out of all the choices, magnesium is the only element.
Answer: Choice 2
14 Which statement describes the components of a mixture?
(1) Each component gains new properties.
(2) Each component loses its original properties.
(3) The proportions of components can vary.
(4) The proportions of components cannot vary.
Solution: In a mixture, the proportion of components can vary. For example, salt and water, could be 50% salt and 50% water or 70% salt and 30% water etc
Answer: Choice 3
January 2019
14 Which substance can not be decomposed by chemical means?
(1) C
(2) CO (3) CO2
(4) C3O2
Solution: Elements can not be broken down by chemical means. The symbols for all elements can be found on the Periodic Table.
Answer:1
39 A mixture consists of ethanol and water. Some properties of ethanol and water are given in the table below.
Which statement describes a property of ethanol after being separated from the mixture?
(1) Ethanol is nonflammable.
(2) Ethanol has a melting point of 0.°C.
(3) Ethanol has a density of 0.80 g/cm3 at STP.
(4) Ethanol has a boiling point of 89°C at standard pressure.
Solution: Let's look at the chart to eliminate some of the answer choices. According to the chart ethanol is flammable, eliminating choice 1. It has a melting point of -114C eliminating choice 2. It has a boiling point of 78C eliminating choice 4. It has a a density of 0.80 g/cm3 according to the chart.
Answer:3
August 2018
8 Which substance can be broken down by chemical means?
(1) ammonia
(2) aluminum (3) antimony
(4) argon
Solution: Elements can not be broken down by a chemical change. Compounds can be broken down by chemical means. We can eliminate all the choices that have elements to arrive at the correct answer. The names of all of the elements can be found in Table S on the Reference Table. Out of all the choices, ammonia is the only compound.
Answer:1
9 Which statement describes H2O(l) and H2O2(l)?
(1) Both are compounds that have the same properties.
(2) Both are compounds that have different properties.
(3) Both are mixtures that have the same properties.
(4) Both are mixtures that have different properties.
Solution:H2O(l) and H2O2(l) are both compounds. Compounds have fixed ratios of atoms. Mixtures consist of multiple substances such as two compounds together. H2O(l) and H2O2(l) are different compounds and should have different properties.
Answer:2
January 2018
7 Chemical properties can be used to
(1) determine the temperature of a substance
(2) determine the density of a substance (3) differentiate between two compounds (4) differentiate between two neutrons
Solution:Chemical properties can be used to differentiate between two compounds. For example one compound may react with water and another might not.
Answer:3
8 Ice, H2O(s), is classified as (1) an ionic compound (2) a molecular compound
(3) a homogeneous mixture
(4) a heterogeneous mixture
Solution:H2O(s) consists of atoms of different elements in fixed proportions representing a compound. A mixture would have multiple substances such as NaCl (aq) ( salt dissolved in water). H2O is composed of nonmetals only and is therefore a molecular compound
Answer:2
14 Which substance can not be broken down by a chemical change?
(1) ammonia
(2) ethanol (3) tungsten
(4) water
Solution: Elements can not be broken down by chemical changes. The names of all of the elements can be found in Table S on the Reference Table.
Answer:3
41 Given the key:
Which particle model diagram represents a chemical change?
Solution: A chemical change occurs when the identity of a substance changes. In choice 4 we go from the molecules with one white circle and two black circles to two different molecules, one with two black circles and another with two white circles.
Answer: 4
43 The arrangement of particles is most ordered in a sample of
(1) NaCl(aq)
(2) NaCl(l) (3) NaCl(g)
(4) NaCl(s)
Solution: Solid(s) particles are more ordered than liquid(l) and liquid particles are more ordered than gas(g).
Answer: 4
June 2018
7 Which statement describes a chemical property of iron? (1) Iron oxidizes. (2) Iron is a solid at STP. (3) Iron melts. (4) Iron is attracted to a magnet.
Solution: A chemical property describes something that changes the identity of a substance. A chemical change represents a reaction. We are looking for a reaction here which is in choice 1. Phase changes such as melting are physical properties.
Answer:1
10 Carbon monoxide and carbon dioxide have
(1) the same chemical properties and the same physical properties
(2) the same chemical properties and different physical properties
(3) different chemical properties and the same physical properties
(4) different chemical properties and different physical properties
Solution:Carbon monoxide and carbon dioxide are two different molecules with different chemical and physical properties.
Answer: 4
12 What is represented by the chemical formula PbCl2(s)? (1) a substance (2) a solution (3) a homogeneous mixture
(4) a heterogeneous mixture
Solution: A mixture consists of multiple substances. PbCl2(s) represents one compound only in solid state, eliminating choices 3 and 4. Solution is a mixture as well, eliminating choice 2.
Answer:1
39 The table below lists properties of selected elements at room temperature.
Based on this table, which statement describes how two of these elements can be differentiated from each other?
(1) Gold can be differentiated from tungsten based on density. (2) Gold can be differentiated from sodium based on malleability. (3) Sodium can be differentiated from tungsten based on conductivity.
(4) Sodium can be differentiated from iodine based on malleability.
Solution: We need to look at the table given to see which answer is correct. Gold and tungsten have the same density and cannot be differentiated, eliminating choice 1. Gold and sodium are both malleable, eliminating choice 2. Sodium and tungsten both have good conductivity, eliminating choice 3. Sodium is malleable but iodine is not.
Answer: 4
40 Which particle diagram represents a mixture?
Solution: A mixture consists of two or more substances (compounds or elements). In choice 3 we see two white circles, representing two atoms of an element and a white circle together with a black circle representing a compound.
Answer: 3
June 2017
21 In which 1.0-gram sample are the particles arranged in a crystal structure? (1) CaCl2(s)
(3) CH3OH(l)
(2) C2H6(g)
(4) CaI2(aq)
Solution: Crystal structure refers to solids (s). Liquids(l), aqueous solutions(aq) and gases (g) take the shape of the container.
Answer:1
41 Which particle diagram represents one substance in the gas phase?
Solution: Gases spread out and take the shape of the container. We can eliminate choices 2 and 4, since they represent a solid. According to the question we are looking for one substance only. One substance means either an element or a compound. Choice 1 has two different substances, one with two white circles and another with two black circles. Choice 3 has one substance only.
Answer: 3
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