CHEM Chapter3. Mass Relations in Chemical Reactions (Homework)

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1 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. There are two different common crystalline forms of carbon diamond and graphite. A less common form called fullerene, C 60, also exists. Different forms of the same element in the same physical state are called: a. allotropes. b. isotopes. c. isomers. d. structural formulas. e. alloforms. 2. A compound contains only magnesium and oxygen. A sample of the compound is determined to contain 3.50 g of magnesium and 2.30 g of oxygen. According to the Law of Definite Proportions, how much magnesium should another sample of this compound contain if it contains 6.91 g of oxygen? a g b g c g d g e g 3. What is the correct classification for OCl? a. polyatomic molecule b. monatomic cation c. polyatomic cation d. monatomic anion e. polyatomic anion 4. Determine the number of sulfur atoms in 27.1 g of molecular sulfur (S 8 ). a b c d e Calculate the formula weight of NaHSO 4. a. 185 amu b. 104 amu c. 193 amu d. 215 amu e. 120 amu 6. A 12.0-gram sample of Cr 2 (SO 4 ) 3 contains how many sulfur atoms? a b c d e

2 7. Which of the following is not a correct description of 16.0 grams of methane, CH 4? a. It is the amount of methane that contains hydrogen atoms. b. It is the amount of methane that contains 12.0 g of carbon. c. It is the amount of methane that contains 4.0 grams of hydrogen. d. It is one mole of methane. e. It is molecules of methane. 8. What is the percent by mass of sulfur in Al 2 (SO 4 ) 3? a. 18.8% b. 35.4% c. 9.38% d. 28.1% e. 24.6% 9. A g sample of a compound contains g of cobalt, g of sulfur, and g of oxygen. What is its simplest formula? a. Co(SO 4 ) 2 b. CoSO 4 c. CoSO 3 d. Co(SO 3 ) 2 e. Co 3 (SO 4 ) What is the empirical formula of an oxide of nitrogen that contains % nitrogen by mass? a. N 2 O b. NO 2 c. NO d. N 2 O 5 e. N 2 O Which of the following samples contains the greatest number of atoms? a g Br b. 7.25g Li c g Zn d g Cs e g Sb 12. How many atoms of chlorine are present in 2.42 grams of boron trichloride, BCl 3? a x atoms b x atoms c x atoms d x atoms e x atoms 13. How many ammonia (NH 3 ) molecules are there in a 115 g sample of ammonia? a x b x c x d x e x

14. What are the empirical and molecular formulas for the following compound? (C = dark atoms, H = light atoms) a. CH (molecular) C 6 H 6 (empirical) c. C 6 H 12 (molecular) CH 2 (empirical) b.

3 14. What are the empirical and molecular formulas for the following compound? (C = dark atoms, H = light atoms) a. CH (molecular) C 6 H 6 (empirical) c. C 6 H 12 (molecular) CH 2 (empirical) b. CH 2 (molecular) C 6 H 12 (empirical) d. C 6 H 6 (molecular) CH (empirical) 15. Which of the following is not a consequence of the Law of Conservation of Matter? a. It can be stated as "matter is neither created nor destroyed during a chemical reaction." b. It means that there will be no observable change in the quantity of matter during a chemical reaction. c. As a result, there will be the same number of moles on both the reactant and the product side of a balanced equation. d. It provides a basis for balancing chemical equations. e. All of these are a consequence of the Law of Conservation of Mass. 16. Balancing a chemical equation so that it obeys the law of conservation of matter requires: a. Keeping the same number of molecules on both sides of the equation. b. Making sure the reactants and products are in the same phase. c. Keeping the total charge the same on both sides of the equation. d. Adjusting the coefficients in front of the formulas so there are the same number and type of atom on both sides of the equation. e. Changing the formulas of the products and reactants. 17. What is the coefficient for carbon dioxide when the following equation showing the combustion of isopropyl alcohol is balanced with the smallest whole number coefficients? C 3 H 8 O + O 2 CO 2 + H 2 O a. 3 b. 4 c. 13 d. 6 e What is the coefficient for HBr when the following equation is balanced with the smallest whole number coefficients? Br 2 + H 2 O HBr + HBrO 3 a. 7 b. 8 c. 6 d. 3 3

4 e Balance the following equation with the smallest whole number coefficients. Choose the answer that is the sum of the coefficients in the balanced equation. Do not forget coefficients of "one". Cr + H 2 SO 4 Cr 2 (SO 4 ) 3 + H 2 a. 15 b. 13 c. 7 d. 11 e Balance the following equation with the smallest whole number coefficients. Choose the answer that is the sum of the coefficients in the balanced equation. Do not forget coefficients of "one". P 4 + Cl 2 PCl 5 a. 15 b. 7 c. 9 d. 13 e What is the sum of all coefficients when the following equation is balanced, using the smallest whole number coefficients? Do not forget coefficients of "one". Cl 2 O 7 + Ca(OH) 2 Ca(ClO 4 ) 2 + H 2 O a. 8 b. 6 c. 5 d. 4 e What is the sum of all coefficients when the following equation is balanced, using the smallest whole number coefficients? Do not forget coefficients of "one". SiCl 4 + H 2 O H 4 SiO 4 + HCl a. 12 b. 6 c. 10 d. 14 e Consider the following balanced equation. 2H 2 + O 2 2H 2 O Which one of the following statements is false? a. The amount of reaction that consumes 32.0 g of O 2 produces 36.0 g of H 2 O. b. One molecule of O 2 will react with 2 molecules of H 2. c. The complete reaction of 2.0 g of H 2 will produce 36.0 g of H 2 O. d. The complete reaction of 32.0 g of O 2 will produce 2 moles of H 2 O. 4

5 e. One mole of O 2 will react with 2 moles of H How many molecules of O 2 would react with 56 C 2 H 6 molecules according to the following balanced equation? 2C 2 H 6 + 7O 2 4CO 2 + 6H 2 O a. 112 b. 50 c. 784 d. 196 e How many moles of O 2 are required to react with 23.5 moles of methanol? 2CH 3 OH + 3O 2 2CO 2 + 4H 2 O a b c d. 40 e Propane (C 3 H 8 ) burns in oxygen to form CO 2 and H 2 O according to the following equation. How many grams of O 2 are required to burn propane molecules? C 3 H 8 + 5O 2 3CO 2 + 4H 2 O a g b. 160 g c g d g e g 27. Acrylonitrile, C 3 H 3 N, is a molecule used to produce a plastic called Orlon. How many grams of acrylonitrile could be produced by reacting 583 g of propene, C 3 H 6 with excess ammonia, NH 3 and oxygen? 2C 3 H 6 + 2NH 3 + 3O 2 2C 3 H 3 N + 6H 2 O a. 368 g b. 735 g c g d. 462 g e. 583 g 28. What mass of SiF 4 could be produced by the reaction of 15 g of SiO 2 with an excess of HF? The equation for the reaction is: SiO 2 + 4HF SiF 4 + 2H 2 O a. 26 g b. 52 g c. 12 g d. 104 g e g 5

6 29. What mass of Li 3 PO 4 can be prepared from the complete reaction of 7.17 grams of LiOH with a stoichiometric amount of H 3 PO 4? 3LiOH + H 3 PO 4 Li 3 PO 4 + 3H 2 O a g b g c g d g e g 30. If a reaction of 5.0 g of hydrogen with 5.0 g of carbon monoxide produced 4.5 g of methanol, what was the percent yield? 2H 2 + CO CH 3 OH a. 63% b. 24% c. 96% d. 11% e. 79% 31. What volume of M NaOH solution contains 53.4 g NaOH? a L b L c L d. 146 L e L 32. The commercial production of phosphoric acid, H 3 PO 4, can be represented by the equation 1540 g 296 g 310 g 1120 g 296 g Ca 3 (PO 4 ) 2 + 3SiO 2 + 5C + 5O 2 + 3H 2 O 3CaSiO 3 + 5CO 2 + 2H 3 PO g/mol 60.1 g/mol 12.0 g/mol 32.0 g/mol 18.0 g/mol The molar mass for each reactant is shown below the reactant, and the mass of each reactant for this problem is given above. Which substance is the limiting reactant? a. H 2 O b. SiO 2 c. C d. O 2 e. Ca 3 (PO 4 ) The number of electrons in a neutral atom of an element is always equal to the of the element. a. Avogadro's number b. atomic number c. atomic mass unit d. mass number e. isotope number 6

7 34. The atomic weight of silver is amu. Naturally occurring silver consists of two isotopes: 107 Ag (mass = amu) and 109 Ag (mass = amu). What percentage of naturally occurring silver is the heavier isotope? a. 52.6% b. 45.4% c. 48.2% d. 51.7% e. 62.7% 35. The element indium has two stable isotopes, indium-113 with an atomic mass of 112.9amu and indium-115 with an atomic mass of 114.9amu. From the atomic weight found on the periodic table for indium, one can conclude that: a. Both isotopes have the same percent natural abundance b. Indium-113 has the highest percent natural abundance c. There is an isotope of indium with an atomic mass of 114.8amu d. Indium-115 has the highest percent natural abundance 36. Octane, C 8 H 18, is a major component of gasoline. Write the balanced formula unit equation for the reaction of the complete combustion of octane. What is the sum of the coefficients? a. 49 b. 17 c. 30 d. 73 e. 61 7

8 Answer Section MULTIPLE CHOICE 1. ANS: A PTS: 1 OBJ: Define allotrope. TOP: Chemical Formulas 2. ANS: A PTS: 1 OBJ: Apply the Law of Definite Proportions. TOP: Chemical Formulas 3. ANS: E PTS: 1 OBJ: Classify a species as a monatomic ion, polyatomic ion, or molecule. TOP: Ions and Ionic Compounds 4. ANS: C PTS: 1 OBJ: Determine the molecular weight of a substance using atomic weights and the chemical formula. Use Avogadro's number, molecular formula, and molecular weight to convert grams to number of atoms. TOP: The Mole 5. ANS: E PTS: 1 OBJ: Determine the formula weight of a substance using atomic weights and the chemical formula. TOP: Formula Weights, Molecular Weights, and Moles 6. ANS: D PTS: 1 OBJ: Determine the formula weight of a substance using atomic weights and the chemical formula. Use Avogadro's number, molecular formula, and formula weight to convert grams to atoms. TOP: Formula Weights, Molecular Weights, and Moles 7. ANS: E PTS: 1 OBJ: Determine the molecular weight of a substance using atomic weights and the chemical formula. Convert grams of a substance to moles, grams of a component, molecules, or atoms. TOP: Formula Weights, Molecular Weights, and Moles 8. ANS: D PTS: 1 OBJ: Calculate percent mass of a component given the chemical formula of the substance. TOP: Percent Composition and Formulas of Compounds 9. ANS: C PTS: 1 OBJ: Derive percent mass from experimental data. Convert percent mass to the simplest formula (empirical formula). TOP: Derivation of Formulas from Elemental Composition 10. ANS: E PTS: 1 DIF: Moderate OBJ: Determine the empirical formula from the percentage composition. TOP: Percent Composition and Formulas of Compounds NOT: Dynamic Question 11. ANS: E PTS: 1 OBJ: Identify the sample with the greatest number of atoms. TOP: Formula Weights, Molecular Weights, and Moles NOT: OWL 12. ANS: A PTS: 1 OBJ: Determine the number of atoms of one atom type in a compound. TOP: Formula Weights, Molecular Weights, and Moles NOT: OWL 13. ANS: A PTS: 1 OBJ: Determine the number of molecules in a sample. TOP: Formula Weights, Molecular Weights, and Moles NOT: OWL 14. ANS: C PTS: 1 OBJ: Determine the empirical and molecular formula given the ball and stick model. TOP: Chemical Formulas NOT: OWL 15. ANS: C PTS: 1 8

9 OBJ: Understand the implications of the Law of Conservation of Matter. 16. ANS: D PTS: 1 OBJ: Understand the implications of the Law of Conservation of Matter. 17. ANS: D PTS: 1 OBJ: Balance a chemical equation. 18. ANS: E PTS: 1 OBJ: Balance a chemical equation. 19. ANS: E PTS: 1 OBJ: Balance a chemical equation. Sum the coefficients. 20. ANS: A PTS: 1 OBJ: Balance a chemical equation. Sum the coefficients. 21. ANS: D PTS: 1 OBJ: Balance a chemical equation. Sum the coefficients. 22. ANS: C PTS: 1 OBJ: Balance a chemical equation. Sum the coefficients. 23. ANS: C PTS: 1 OBJ: Translate a balanced chemical equation into words. TOP: Calculations Based on Chemical Equations 24. ANS: D PTS: 1 OBJ: Use the balanced chemical reaction to convert molecules organic reactant to molecules dioxygen. TOP: Calculations Based on Chemical Equations 25. ANS: A PTS: 1 OBJ: Use the balanced chemical reaction to convert moles organic reactant to moles dioxygen. TOP: Calculations Based on Chemical Equations 26. ANS: C PTS: 1 OBJ: Use Avogadro's number, molecular weights, and the balanced chemical reaction to convert molecules organic reactant to grams dioxygen. TOP: Calculations Based on Chemical Equations 27. ANS: B PTS: 1 OBJ: Use molecular weights and the balanced chemical reaction to convert grams organic reactant to grams product. TOP: Calculations Based on Chemical Equations 28. ANS: A PTS: 1 OBJ: Use molecular weights, formula weights, and the balanced chemical reaction to convert grams reactant to grams product. TOP: Calculations Based on Chemical Equations 29. ANS: B PTS: 1 OBJ: Use formula weights and the balanced chemical reaction to convert grams reactant to grams product. TOP: Calculations Based on Chemical Equations 30. ANS: E PTS: 1 DIF: Harder Question OBJ: Use molecular weights and the balanced chemical equation to determine the limiting reactant. Use the limiting reactant, molecular weights, and the balanced chemical reaction to determine the theoretical yield. Calculate the percent yield given the actual yield. TOP: Percent Yields from Chemical Reactions 31. ANS: E PTS: 1 OBJ: Calculate volume of solution given grams solute and solution molarity. TOP: Concentrations of Solutions 32. ANS: B PTS: 1 DIF: Moderate OBJ: Identify the limiting reactant. TOP: The Limiting Reactant Concept NOT: Dynamic Question 9

10 33. ANS: B PTS: 1 OBJ: Know the definition of atomic number. Understand the relationship of atomic number to the number of electrons in a neutral atom. TOP: Atomic Number 34. ANS: C PTS: 1 OBJ: Use atomic mass and atomic weight to calculate isotopic abundance. TOP: The Atomic Weight Scale and Atomic Weights 35. ANS: D PTS: 1 OBJ: Identify the isotope with the greatest percent abundance based on atomic weight. TOP: The Atomic Weight Scale and Atomic Weights NOT: OWL 36. ANS: E PTS: 1 OBJ: Write a balanced chemical equation for the combustion of a hydrocarbon in excess oxygen. Sum the coefficients. TOP: Oxygen and the Oxides 10

General Chemistry 1 CHM201 Unit 2 Practice Test

General Chemistry 1 CHM201 Unit 2 Practice Test 1. Which statement about the combustion of propane (C 3H 8) is not correct? C 3H 8 5O 2 3CO 2 4H 2O a. For every propane molecule consumed, three molecules