12 Chemistry 2012 class Mole calculations and gravimetric analysis: test #1 Date: Tuesday 7 February 2012 Q1. Which of the following is an empirical formula? A. B. C. D. H2SO4 C2H6 CH3COOH P4O10 0% A. 0% B. 0% C. 0% D. Q2. In an analysis of a gas, the mass of 5.00L at STP was found to be 13.1g. Which of the following is the gas most likely to be? A. B. C. D. Cl2 H2 CO2 SO2 0% A. 0% B. 0% C. 0% D. Q3. Consider the following equation: 2Al(s) + Cr2O3(s) → Al2O3(s) + 2Cr(s) What is the theoretical yield of chromium that can be produced by the reaction of 40.0g of Cr2O3 with 8.00g of aluminium? A. B. C. D. 7.70g 15.4g 27.3g 30.8g 0% A. 0% B. 0% C. 0% D. Q4. The largest number of hydrogen atoms will be present in: A. 0.40 mol of NH4Cl B. 200mL of 5M HNO3 C. 18g of glucose (C6H12O6) where M = 180 g mol-1 D. 0.60 mol of hydrogen gas 0% 1 0% 2 0% 3 0% 4 Q5. A hydrocarbon has an empirical formula of CH2 and a molecular mass of 56. The molecular formula of the molecule is: A. B. C. D. CH2 C2H4 C3H6 C4H8 0% A. 0% B. 0% C. 0% D. Q6. A bottle of bleach contains 43g of sodium hypochlorite (NaOCl) per litre of solution. This concentration is equivalent to: A. B. C. D. 43% m/m 43 ppm 0.058 mol per litre 0.58 M 0% A. 0% B. 0% C. 0% D. Q7. In a gravimetric analysis of fertiliser a student precipitated barium sulfate to analyse for sulfate ions , but her calculated result was higher than expected. This error could be due to: A. some of the precipitate went through the filter paper. B. the student did not dry the precipitate sufficiently. C. some of the precipitate remained in the beaker. D. the student did not use excess barium ions. 0% A. 0% B. 0% C. 0% D. Q8. When performing a gravimetric analysis, a student forgot to wash the precipitate with deionised water. The final result will be: A. Unchanged. B. Smaller than it should have been. C. Larger than it should have been. D. Any effect will depend on the chemical formula of the precipitate formed. 0% 1 0% 2 0% 3 0% 4 Q9. A gravimetric analysis was used to determine the amount of salt (sodium chloride) in a packet of noodles. An appropriate precipitating agent to use would be: A. B. C. D. Hydrochloric acid. Silver nitrate. Magnesium hydroxide. Potassium sulfate. 0% 1 0% 2 0% 3 0% 4 Q10. Which of the following experimental procedure errors will NOT have any effect on the calculated mass of the element under investigation? A. The precipitate was still wet when it was weighed. B. More than one compound was present that reacted with the precipitating agent. C. The student used gravity to remove the filtrate from the precipitate rather than vacuum filtration D. The filter paper has a small hole in it. 0% A. 0% B. 0% C. 0% D.