2. In which of these compounds are there twice as many oxygen atoms as hydrogen atoms? a. H 3 PO 4 c. HClO 3 b. H 2 SO 4 d. H 2 O

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1 Test Review Unit 3_3: Law of conservation of mass Identify the letter of the choice that best completes the statement or answers the question. At the end of the file you can find chemical equations to be balanced and their solutions. 1. How many atoms of oxygen, O, are required to form two molecules of sulfuric acid, H 2 SO 4? a. 2 c. 6 b. 4 d In which of these compounds are there twice as many oxygen atoms as hydrogen atoms? a. H 3 PO 4 c. HClO 3 b. H 2 SO 4 d. H 2 O 3. The molecule of glucose has the following formula: C 6 H 12 O 6. If we read 2C 6 H 12 O 6, how many atoms of oxygen are there, according to this chemical expression? a. 2 c. 12 b. 6 d The equation below represents a chemical reaction that occurs in living cells. It is, called respiration. C 6 H 12 O O 2 6 CO2 + 6 H 2 O How many atoms are represented in the reactants of this equation? a. 6 c. 24 b. 12 d Nitrogen dioxide is a gas that can be generated by emissions from vehicles and factories. It can also be generated by natural sources, such as forest fires, lightning, and microbial activity in soil. The equation for producing nitrogen dioxide is shown below. 2 NO + O 2 2 NO 2 Colorless gas Colorless gas Brown gas Which of these provides evidence that a chemical reaction occurs? a. A gas is present. c. The state of matter remains the same. b. The total number of atoms remains unchanged. d. A brown gas is produced. During respiration, oxygen reacts with glucose forming carbon dioxide and water. Which is the correct word equation for respiration? a. glucose + oxygen carbon dioxide + water b. glucose + carbon dioxide oxygen + water c. carbon dioxide + water glucose + oxygen d. oxygen + water glucose + carbon dioxide 7. Fireworks contain many different chemicals. For example, lithium carbonate is commonly used to give a red colour to fireworks. On the other hand, magnesium is added to fireworks as it produces a very bright white light when it reacts with oxygen. Magnesium oxide is made in this reaction. Complete the word equation to show the reactants and products.

2 a. Lithium + Carbonate Red colour b. Magnesium + Lithium Magnesium oxide c. Magnesium + Oxygen Magnesium oxide d. Magnesium oxide Magnesium + Oxygen 8. When methane burns in a plentiful supply of air, the products are a. carbon and water c. carbon monoxide and water b. carbon dioxide and water d. carbon dioxide and hydrogen 9. 2C 2 H 2 (g) + 5O 2 (g) 4 CO 2 (g) + Which additional product balances this reaction? a. 4OH (aq) c. H 2 O 2 (g) b. CH 4 (g) d. 2H 2 O(g) HCl (aq) PbCl2 (s) + Cl 2 (g) + 2 H 2 O(l) + The partial chemical equation above represents a way to obtain lead(ii) chloride. What is the missing reactant? a. PbO(s) c. PbO 2 (s) b. Pb(s) d. PbCl 4 (s) 11. All the following reactions are correctly balanced except : a. 2C 2 H O 2 4 CO2 + 2 H 2 O c. NaHCO 3 Na 2 CO 3 + H 2 O + CO 2 b. 4 Fe + 3 O 2 2 Fe2O 3 d. 2CH 3 OH + 3 O 2 2 CO2 + 4 H 2 O 12. Mg + HCl MgCl2 + H 2 When the above equation is balanced, the coefficient for magnesium chloride is a. 0 c. 2 b. 1 d PbO 2 PbO + O2 What are the coefficients that will balance this chemical equation? a. 2, 1, 1 c. 2, 2, 1 b. 3, 4, 2 d. 4, 3, K + H 2 O KOH + H2 What is the coefficient for H 2 O when the above equation is balanced? a. 1 c. 3 b. 2 d. 4

15. Aluminum metal and oxygen gas combine to produce aluminum oxide (Al 2 O 3 ). Which of these is the balanced equation for this reaction? a. Al + O 2 Al 2 O 3 c. 2Al + 3O 2 5Al2O 3 b.

3 15. Aluminum metal and oxygen gas combine to produce aluminum oxide (Al 2 O 3 ). Which of these is the balanced equation for this reaction? a. Al + O 2 Al 2 O 3 c. 2Al + 3O 2 5Al2O 3 b. 2Al + 2O 2 2Al2O 3 d. 4Al + 3O 2 2Al2O Ca(C 2 H 3 O 2 ) 2 + K 3 PO 4 Ca 3 (PO 4 ) 2 + KC 2 H 3 O 2 Which set of coefficients balances the equation? a. 3, 3, 1, 2 c. 3, 2, 1, 6 b. 6, 1, 1, 3 d. 6, 2, 1, What coefficient values will balance the reaction shown above? a. 2, 2, 1 c. 2, 1, 2 b. 1, 1, 1 d. 1, 2, 2 Which chemical equation supports the law of conservation of mass? a. 2H 2 O(l) + H 2 (g) O 2 (g) b. Zn(s) + HCl(aq) ZnCl 2 (aq) +H 2 (g) c. Al 4 C 3 (s) +H 2 O(l) CH 4 (g) + Al(OH) 3(s) d. CH 4 (g) +2O 2 (g) CO 2 (g) +2H 2 O(g) In the procedure shown above, a calcium chloride solution is mixed with a sodium sulfate solution to create the products shown. Which of the following is illustrated by this activity? a. The law of conservation of mass c. The law of conservation of momentum b. The theory of thermal equilibrium d. The theory of covalent bonding A substance with a mass of 10 g is heated to produce two new substances. The mass of the first new substance is 9.3 g and the mass of the second new substance is 0.7 g. Which of the following is best demonstrated by this example? a. heat transfer c. law of conservation of mass

4 b. physical change d. law of conservation of energy 21. CaCO 3 CaO + CO 2 The chemical equation shows CaCO 3 being heated. Which of these statements best describes the mass of the products if 100 g of CaCO 3 is heated? a. The difference in the products masses is equal to the mass of the CaCO 3. b. The sum of the products masses is less than the mass of the CaCO 3. c. The mass of each product is equal to the mass of the CaCO 3. d. The sum of the products masses equals the mass of the CaCO A chemical reaction in which calcium carbonate, CaCO 3, is decomposed results in the production of two simpler compounds. CaCO 3 CaO + CO 2? g g g What mass of calcium carbonate, to the nearest hundredth of a gram, is decomposed in this reaction? a g c g b g d g 23. According to the law of conservation of mass, how much zinc is obtained? a. 40 g c. 104 g b. 88 g d. 256 g 24. 2Cu + O 2 2CuO When 127 g of copper reacts with 32 g of oxygen gas to form copper (II) oxide, no copper or oxygen is left over. How much copper (II) oxide is produced? a. 32 g c. 127 g b. 95 g d. 159 g The mass of a rusty bicycle is found to be slightly greater than the mass of the same bicycle before it rusted. The change in mass indicates that the rusting process a. is a physical change c. decreases the density of the metal b. involves an energy-to-matter conversion d. involves metal bonding with other atoms

Copper (Cu) and sulfur (S) were heated in a covered container. After the reaction was complete, the unreacted sulfur was removed. The table contains the results of the investigation.

5 Copper (Cu) and sulfur (S) were heated in a covered container. After the reaction was complete, the unreacted sulfur was removed. The table contains the results of the investigation. How much sulfur, in grams, failed to react with the copper? a g c. 1,85 g b. 1,61 g d. None of the above 27. Given the balanced equation representing a reaction: 2H 2 + O 2 2H2O + energy Which mass of oxygen completely reacts with 4.0 grams of hydrogen to produce 36.0 grams of water? a. 8.0 g c g b g d g 28. The illustrations show a conservation-of-mass experiment. The solution in the beaker lost mass because a. materials have less mass at high temperatures c. sodium sulfate (Na 2 SO 4 ) is lighter than air b. the mass of the reactants and products was less than 100 g d. some of the water molecules turned into gas

7 Test Review Unit 3. Answers

8 Balancing chemical reactions

10 Key

12 c 1. When marking a student s report on coal, the teacher circled two errors. The marked report is shown. Give the correct answers for errors 1 and 2. a. 1: a natural resource. 2: sulfur oxide b. 1: Biological material 2: carbon dioxide c. 1: non-renewable resource 2: carbon dioxide d. None of the above

13 b 2. a 3. Which statement about carbon dioxide in air is thought to be false? The increase in the level of carbon dioxide in the air may a. cause global warming c. be due to increased burning of fossil fuels b. cause the atmosphere to cool down d. be due to the extensive clearing of forests. Which of the following are both fossil fuels? a. Oil and peat c. Coal and hydrogen b. Oil and petrol d. Natural gas and ethanol c 4.Which statement is correct? a. Carbon dioxide in the air is not a cause of the greenhouse effect. b. Burning petrol decreases carbon dioxide levels in the atmosphere. c. Clearing forests causes the carbon dioxide levels in the air to increase. d. Increasing levels of carbon dioxide in the air are causing the atmosphere to cool a 5. Which of the following gases in the atmosphere will cause the greenhouse effect? a. Carbon dioxide c. Oxygen b. Sulphur dioxide d. Nitrogen Test Review Unit 3. Answers

C2.6 Quantitative Chemistry Foundation

C2.6 Quantitative Chemistry Foundation 1. Relative masses Use the periodic table to find the relative masses of the elements below. (Hint: The top number in each element box) Hydrogen Carbon Nitrogen Oxygen