Stoichiometry Review. 1. Given the formula for a compound: 4. What is the chemical formula for zinc carbonate?

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1 1. Given the formula for a compound: 4. What is the chemical formula for zinc carbonate? Which molecular formula and empirical formula represent this compound? A) C2HNO2 and CHNO B) C2HNO2 and C2HNO2 C) C4H2N2O4 and CHNO D) C4H2N2O4 and C2HNO2 2. Given two formulas representing the same compound: Formula A CH3 Formula B C2H6 Which statement describes these formulas? A) Formulas A and B are both empirical. B) Formulas A and B are both molecular. C) Formula A is empirical, and formula B is molecular. D) Formula A is molecular, and formula B is empirical. 3. Given the formulas of four organic compounds: A) ZnCO3 B) Zn(CO3)2 C) Zn2CO3 D) Zn3CO2 5. What is the gram-formula mass of (NH4)3PO4? A) 112 g/mol B) 121 g/mol C) 149 g/mol D) 242 g/mol 6. The gram-formula mass of a compound is 48 grams. The mass of 1.0 mole of this compound is A) 1.0 g B) 4.8 g C) 48 g D) 480 g 7. A compound has a molar mass of 90. grams per mole and the empirical formula CH2O. What is the molecular formula of this compound? A) CH2O B) C2H4O2 C) C3H6O3 D) C4H8O4 8. What is the empirical formula of a compound that contains 28% iron, 24% sulfur, and 48% oxygen by mass? A) FeSO3 B) FeSO4 C) Fe2(SO3)3 D) Fe2(SO4)3 9. Which compound has the smallest percent composition by mass of chlorine? A) HCl B) KCl C) LiCl D) NaCl 10. What is the percent composition by mass of sulfur in the compound MgSO4 (gram-formula mass = 120. grams per mole)? A) 20% B) 27% C) 46% D) 53% 11. In which type of chemical reaction do two or more reactants combine to form one product, only? A) synthesis B) decomposition C) single replacement D) double replacement Which compounds have the same molecular formula? A) A and B B) A and C C) D and B D) D and C

2 12. Given the balanced equations representing two chemical reactions: Cl2 + 2NaBr 2NaCl + Br2 2NaCl 2Na + Cl2 Which type of chemical reactions are represented by these equations? A) single replacement and decomposition B) single replacement and double replacement C) synthesis and decomposition D) synthesis and double replacement 13. Given the balanced equation representing a reaction: Which type of reaction is represented by this equation? A) decomposition B) double replacement C) single replacement D) synthesis 14. Given the incomplete equation representing a reaction: 2C6H14 + O2 12CO2 + 14H2O What is the coefficient of O2 when the equation is completely balanced using the smallest whole-number coefficients? A) 13 B) 14 C) 19 D) Given the incomplete equation representing a reaction: What is the formula of the missing product? A) B) C) D) 16. Given the balanced equation representing a reaction: C3H8(g) +5O2(g) 3CO2(g) + 4H2O(g) What is the total number of moles of O2(g) required for the complete combustion of 1.5 moles of C3H8(g)? A).30 mol B) 1.5 mol C) 4.5 mol D) 7.5 mol 17. Given the balanced equation representing a reaction: CaO(s) + CO2(g) CaCO3(s) + heat What is the total mass of CaO(s) that reacts completely with 88 grams of CO2(g) to produce 200. grams of CaCO3(s)? A) 56 g B) 88 g C) 112 g D) 288 g 18. At STP, 4 liters of O2 contains the same total number of molecules as A) 1 L of NH3 B) 2 L of Cl2 C) 8 L of He D) 4 L of CO2

3 Base your answers to questions 19 and 20 on The equation below represents the reaction between 1-butene and bromine to form the compound 1,2-dibromobutane, C4H8Br Write the empirical formula for the product. 20. Determine the gram-formula mass of 1-butene. Base your answers to questions 21 through 23 on John Dalton, an early scientist, sketched the structure of compounds using his own symbols for the elements known at the time. Dalton's symbols for four elements and his drawing of potassium aluminum sulfate are represented by the diagram below. Today, it is known that the chemical formula for potassium aluminum sulfate is. It is a hydrated compound because water molecules are included within its crystal structure. There are 12 moles of H2O for every 1 mole of. The compound contains two different positive ions. The gram-formula mass of is 474 grams per mole. 21. Show a numerical setup for calculating the percent composition by mass of water in. 22. Describe, in terms of composition, one way in which Dalton s perception of potassium aluminum sulfate differs from what is known today about the compound.

4 23. Identify one positive ion in the hydrated compound. Your response must include both the chemical symbol and charge of the ion. Base your answers to questions 24 through 27 on The reaction between aluminum and an aqueous solution of copper(ii) sulfate is represented by the unbalanced equation below. Al (s) + CuSO4(aq) Al2(SO4)3(aq) + Cu(s) 24. Determine the total mass of Cu produced when 1.08 grams of Al reacts completely with 9.58 grams of CuSO4 to produce 6.85 grams of Al2(SO4) Explain why the equation represents a chemical change. 26. Balance the equation below, using the smallest whole-number coefficients. Al(s) + CuSO4(aq) Al2(SO4)3(aq) + Cu(s) 27. Identify the type of chemical reaction represented by the equation. Base your answers to questions 28 through 30 on Vitamin C, also known as ascorbic acid, is water soluble and cannot be produced by the human body. Each day, a person's diet should include a source of vitamin C, such as orange juice. Ascorbic acid has a molecular formula of C6H8O6 and a gram-formula mass of 176 grams per mole. 28. Write the empirical formula for ascorbic acid. 29. Show a numerical setup for calculating the percent composition by mass of oxygen in ascorbic acid. 30. Determine the number of moles of vitamin C in an orange that contains gram of vitamin C. Base your answers to questions 31 and 32 on In a titration, a few drops of an indicator are added to a flask containing 35.0 milliliters of HNO3(aq) of unknown concentration. After 30.0 milliliters of 0.15 M NaOH(aq) solution is slowly added to the flask, the indicator changes color, showing the acid is neutralized. 31. Complete the equation below for this neutralization reaction by writing the formula of each product. HNO3(aq) + NaOH(aq) The volume of the NaOH(aq) solution is expressed to what number of significant figures?

5 Base your answers to questions 33 through 35 on A total of 1.4 moles of sodium nitrate is dissolved in enough water to make 2.0 liters of an aqueous solution. The gram-formula mass of sodium nitrate is 85 grams per mole. 33. Show a numerical setup for calculating the mass of the solute used to make the solution. 34. Write the chemical formula for the solute in the solution. 35. Compare the boiling point of the solution at standard pressure to the boiling point of H 2O at standard pressure.

6 Answer Key Stoichiometry Review 1. D 2. C 3. B 4. A 5. C 6. C 7. C 8. D 9. B 10. B 11. A 12. A 13. C 14. C 15. C 16. D 17. C 18. D 19. C2H4Br g/mol —Dalton s drawing did not include the element hydrogen. —He perceived 5 sulfur atoms, but the formula actually has 2 sulfur atoms. — Dalton s drawing had more aluminum. —It did not include water. 23. K + Al g 25. — The products are different substances with different properties from the reactants. — There is a loss and gain of electrons by substances in the reaction Al(s) + 3 CuSO4(aq) Al2(SO4)3(aq) + 3 Cu(s) 27. single replacement redox 28. C3H4O mol or mol 31. NaNO3(aq) + H2O( ) or HOH + NaNO or three 33. —(85 g/mol)(1.4 mol) —(1.4)(85) 34. NaNO3 35. —At standard pressure, the boiling point of the solution is higher than the boiling point of H2O. —Water boils at a lower temperature.