Chemistry 120 – October Exam – 2010 Page 2
Chemistry 120
October Exam
Name:______
October 2012 I. D. #: ______
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This exam should contain 5 different questions plus a Periodic Table. If it does not, notify the Instructor immediately. ALL QUESTIONS ARE OF EQUAL VALUE.
Answer all the questions in the space provided. Relevant information can be found below or on the Periodic Table.
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DATA
Avogadro's Number N = 6.022 × 1023
PV = nRT Gas Constant R = 0.08206 L atm K-1 mol-1
0.00°C = 273.15 K
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1. Washing soda, a compound can be written as Na2CO3.xH2O, where x is the number of moles of H2O per mole of Na2CO3. When a sample of 2.558 g of washing soda is heated at 125°C , all the water of hydration is lost leaving 0.948 g of Na2CO3.
(a) What is the value of x? (show your work) (6)
(b) Calculate the mass percent and the mole percent of C in a 100 g sample of Na2CO3 (4)
2. (a) Balance the following redox equation:
V2O3 + KMnO4 + H2SO4 ® V2O5 + K2SO4 +MnSO4 +H20 (7)
(b) Write the oxidation reaction and indicate the oxidizing agent (3)
3. (a) Provide ystematic (IUPAC) names for the following compounds: (6)
(i) Fe(OH)2 (iv) IF5
(ii) HBrO3 (v) NaC
(iii) KMnO4 (vi) CoC2×6H2O
(b) Provide chemical formulas for the following: (4)
(i) copper (II) perchlorate (iii) zinc nitrate
(ii) mercury (I) bromide (iv) calcium hydrogen carbonate
4. The questions that follow apply to the compounds ethanol and ethane
(a) What is the molecular formula and empirical formula for ethane and ethanol? (4)
(b) Write a balanced equation for the combustion of ethane (3)
(c) If there are x moles before the reaction and if all the ethane is converted to products,
is it possible to have x + 1 moles in the reaction chamber, (you may assume all products and
reactants are gases and the system is closed) explain (3) – bonus +2 for exceptional answers.
5. In the following reaction that we looked at in class,
2NaN3 (s) ® 2Na (l) + 3N2 (g)
(a) How many moles of N2 are produced by the decomposition of 2.50 mol of NaN3 ?
(b) How many grams of NaN3 are required to form 6.00 g of nitrogen gas?
(c) How many grams of NaN3 are required to produce 10.0 ft3 of nitrogen gas if the gas has a density of 1.25 g/L?