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.H 2 SO 4 B.C 2 H 6 C.CH 3 COOH D.P 4 O 10

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.Cl 2 B.H 2 C.CO 2 D.SO 2

Q3. Consider the following equation: 2Al(s) + Cr 2 O 3 (s) → Al 2 O 3 (s) + 2Cr(s) What is the theoretical yield of chromium that can be produced by the reaction of 40.0g of Cr 2 O 3 with 8.00g of aluminium? A.7.70g B.15.4g C.27.3g D.30.8g

Q4. The largest number of hydrogen atoms will be present in: A.0.40 mol of NH 4 Cl B. 200mL of 5M HNO 3 C. 18g of glucose (C 6 H 12 O 6 ) where M = 180 g mol -1 D mol of hydrogen gas

Q5. A hydrocarbon has an empirical formula of CH 2 and a molecular mass of 56. The molecular formula of the molecule is: A.CH 2 B.C 2 H 4 C.C 3 H 6 D.C 4 H 8

Q6. A bottle of bleach contains 43g of sodium hypochlorite (NaOCl) per litre of solution. This concentration is equivalent to: A.43% m/m B.43 ppm C mol per litre D.0.58 M

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.

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.

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.Hydrochloric acid. B.Silver nitrate. C.Magnesium hydroxide. D.Potassium sulfate.

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.