Chemistry Past Papers Chapter 4

CHAPTER 4 1. Consider the unbalanced chemical equation: H3PO4 (aq) + Ba(OH)2 (aq) → Ba3(PO4)2 (S) + H2O A volume of 46.0 mL of aqueous Ba(OH)2 solution was required to react completely with 0.685 g H3PO4 (molar mass = 98.0 g/mol) to produce Ba3(PO4)2. Calculate the molar concentration of the Ba(OH)2 solution. A)0.552 M B)0.228 M C)0.403 M D)0.328 M E) 0.655 M 2. If 318.0 mL of nitrogen gas measured at 488.9 mmHg and 22.3oC, reacts with excess iodine according to the following reaction, what mass of nitrogen triiodide (molar mass = 394.72) is produced? (1 atm = 760 mmHg and k = oC + 273) N2 (g) + 3I2 (S) → 2NI3 (S) A) 3.33 g B) 4.33 g C) 13.30 g D) 20.0 g E) 6.65 g P a g e 21 | 45 3. Consider the unbalanced chemical equation: H2SO4 (aq) + Fe(OH)3 (S) → Fe2(SO4)3 (S) + H2O (L) A volume of 38.0 mL of aqueous H2SO4 solution was required to react completely with 0.685 g Fe(OH)3 (molar mass = 106.8 g/mol) to produce Fe2(SO4)3. Calculate the molar concentration of the H2SO4 solution. A) 0.253 M B) 0.344 M C) 0.214 M D) 0.301 M E) 0.175 M 4. When 12.0 g of Ca3(PO4)2 and 12.0 g of H2SO4 were allowed to react according to the following equation, 6.00 g of CaSO4 were produced. Calculate the % yield of CaSO4. Molar masses (g/mol): Ca3(PO4)2 = 310.2; H2SO4 = 98.1; CaSO4 = 136.1 and H3PO4 = 98.0 Ca3(PO4)2 (S) + 3 H2SO4 (aq) → 3 CaSO4 (S) + 2 H3PO4 (aq) A) 63.3 B) 76.0 C) 88.6 D) 38.0 E) 50.6 P a g e 22 | 45 5. Which of the following salts is insoluble in water? A) CuSO4 B) BaCO3 C) CaCl2 D) Pb(NO3)2 E) Ba(OH)2 6. Which of the following compounds is a nonelectrolyte? A) KOH (aq) B) acetic acid, CH3COOH (aq) C) methanol, CH3OH (aq) D) sulfuric acid, H2SO4 (aq) E) ammonia, NH3 (aq) 7. Tetra phosphorus hexoxide P4O6 (molar mass = 219.9 g/mol) is formed by the following reaction: P4 (s) + 3O2 (g) → P4O6 (s) If a mixture of 38.7 g of oxygen (molar mass = 32 g/mol) and excess phosphorus actually produce 54.3 g of P4O6. What is the percent yield for the reaction? A) 61.3% B) 48.8% C) 26.3% D) 77.5% E) 37.6% P a g e 23 | 45 8. Magnesium reacts with iron (III) chloride to form magnesium chloride and iron. 3Mg (s) + 2FeCl3 (s) → 3MgCl2 (s) + 2Fe (s) A mixture of 41.0 g of magnesium (molar mass = 24.31 g/mol) and 145 g of iron (III) chloride (molar mass = 162.2 g/mol) is allowed to react. What mass of magnesium chloride MgCl2 (molar mass = 95.21 g/mol) is formed? A) 136 g B) 161 g C) 146 g D) 128 g 9. Calculate the molarity of solution prepared by diluting 165 mL of 0.700 M calcium chloride to 900.0 mL. A) 3.86 M B) 0.138 M C) 0.182 M D) 0.128 M 10. How much of 1.20 M NaOH will be needed to neutralize 168 mL of 3.0 M H2SO4? A) 1.8 L B) 0.042 L C) 0.84 L D) 0.090 L P a g e 24 | 45 11. What is the oxidation number for Platinum in (PtCl6)-2 A) -2 B) +4 C) -4 D) +1 E) +6 12. Calculate the oxidation number of sulfur , S , in the formula Na2S2O7: A) -2 B) +2 C) +4 D) +5 E) +6 13. Calculate the number of moles of sodium hydroxide in 2.45 L of 1.78 M NaOH solution. A) 4.36 mol B) 4.04 mol C) 1.72 mol D) 3.29 mol E) 2.16 mol P a g e 25 | 45 14. Which of the following compounds is insoluble in water? A) Na2CO3 B) FeCO3 C) (NH4)2CO3 D) Na2S E) AgNO3 15. In the following reaction, what are the spectator ions? Pb(NO3)2 (aq) + 2NaCl (aq) → PbCl2 (S) + 2NaNO3 (aq) A) Na+ (aq) and Cl- (aq) B) Pb+2 (aq) and Cl- (aq) C) Pb+2 (aq) and NO3- (aq) D) Na+ (aq) and NO3E) NO3- (aq) and Cl- (aq) 16. Which of the following is a weak acid? A) H2SO4 B) HNO3 C) HCL D) HNO2 E) HBr P a g e 26 | 45 17. Which of the following reaction is an acid-base reaction? A) NaCl (aq) + AgNO3 → AgCl (S) + NaNO3 (aq) B) Cl2 (g) + 2HI (g) → 2HCl (g) + I2 (g) C) CH4 (g) + 2O2 (g) → 2H2O (L) + CO2 (g) D) Na2CO3 (S) + 2HCl (aq) → H2O (l) + CO2 (g) + 2NaCl (aq) E) Ba(OH)2 (aq) + Na2SO4 (aq) → BaSO4 (S) + 2NaOH (aq) 18. How many millilitres of 10.0 M HCl must be diluted to obtain 1.0 litter of 6.0 M HCL? A) 375 mL B) 300 mL C) 260 mL D) 600 mL E) 450 mL 19. Which one of the following compounds is a strong electrolyte in aqueous solution? A) H2O B) NaCl C) HF D) CH3COOH E) NH3 P a g e 27 | 45 20. Which of the following solutions has the least electrical conductance? A) KNO (aq) B) (NH2)2CO C) NaCl (aq) D) LiOH (aq) E) H2SO4 (aq) P a g e 28 | 45