NO SOLUTIONS Y12 Unit 1 Test 2 1.2 AMOUNT OF SUBSTANCE Bonne Chance!Name: Answer all questions Total 50 marks

SECTION A TOTAL ../35 SECTION B TOTAL /15 TOTAL ./50 = ..% Grade __________

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1.

(a) A student added some dilute sulphuric acid is added to a solution of sodium hydroxide in a test-tube. Write an ionic equation for the reaction that occurred. ...................................................................................................................................(1)

(b) The student then added some barium chloride solution into the same test-tube, and observed a white precipitate. Write an ionic equation for the reaction that occurred, including state symbols. ..................................................................................................................................... .....................................................................................................................................(2) (Total 3 marks)

2.(a) Give the meaning of the term empirical formula. ..................................................................................................................................... .....................................................................................................................................(1)

(b)

Define the term relative molecular mass. ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(c)

The empirical formula of a compound is CHO and its relative molecular mass has the value 174. Determine the molecular formula of this compound and show your working. ..................................................................................................................................... .....................................................................................................................................(2)

(d)

A compound with molecular formula CH4O burns in air to form carbon dioxide and water. Write a balanced equation for this reaction. .....................................................................................................................................(1) (Total 6 marks)

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3. (a) Nitromethane, CH3NO2, burns in oxygen forming three gases.

1 2CH3NO2(l) + 1 2 O2(g) 2CO2(g) + 3H2O(g) + N2(g)(i) A 100g sample of nitromethane was completely burned in oxygen. Calculate the number of moles of nitromethane that were burned and also calculate the total volume of gaseous products at 400K and l00kPa. Moles of nitromethane. .................................................................................... .......................................................................................................................... Total volume of gaseous products. .................................................................. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (ii) The combustion reaction is very exothermic and heats the products to a temperature of 1000 K. Calculate the total volume of gaseous products at this temperature and 100 kPa. .......................................................................................................................... ..........................................................................................................................(7)

(b)

A 153 kg sample of ammonia gas, NH3, was compressed at 800 K into a cylinder of volume 3.00 m3. (i) Calculate the pressure in the cylinder assuming that the ammonia remained as a gas. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................

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(ii)

Calculate the pressure in the cylinder when the temperature is raised to 1000K. ........................................................................................................................... ...........................................................................................................................

(iii)

Calculate the molarity of the solution formed by dissolving this mass of ammonia in water to make 1.0 m3 of solution. ........................................................................................................................... ...........................................................................................................................(7) (Total 14 marks)

4. (a) Calculate the empirical formula of an oxide of nitrogen which contains 25.9% of nitrogen by mass. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................(3)

(b)

The molecular formula of the oxide in part (d) is the same as its empirical formula. The oxide decomposes on warming to produce nitrogen dioxide and oxygen. Write an equation for the decomposition reaction. ...................................................................................................................................(1) (Total 4 marks)

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5. (a) Sodium carbonate is produced in large quantities by the Solvay Process. In this process, ammonia and carbon dioxide are passed through a solution of sodium chloride, forming sodium hydrogencarbonate and ammonium chloride. NaCl + NH3 + CO2 + H2O NaHCO3 + NH4Cl In the next stage, sodium hydrogencarbonate is thermally decomposed to form sodium carbonate. 2NaHCO3 Na2CO3 + H2O + CO2 Calculate the maximum mass of sodium carbonate which, theoretically, could be obtained from 546 kg of sodium chloride.

(4)

(b)

100 cm3 of a standard solution of Na2CO3 was produced by dissolving 0.537 g of Na2CO3 in water in a volumetric flask. Calculate the concentration, in mol dm3, of the Na2CO3 solution.

(2)

(c)

Carbon dioxide gas can be absorbed by sodium hydroxide solution, as shown by the following equation. 2NaOH(aq) + CO2(g) Na2CO3(aq) + H2O(l) Calculate the concentration in mol dm3 of sodium carbonate in a solution formed by dissolving 2.00g of carbon dioxide in 200 cm3 (an excess) of aqueous sodium hydroxide. ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

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6.

The chloride of an element Z reacts with water according to the following equation. ZCl4(l) + 2H2O(l) ZO2(s) + 4HCl(aq) A 1.304 g sample of ZCl4 was added to water. The solid ZO2 was removed by filtration and the resulting solution was made up to 250 cm3 in a volumetric flask. A 25.0 cm3 portion of this solution was titrated against a 0.112 mol dm3 solution of sodium hydroxide, of which 21.7 cm3 were required to reach the end point. Use this information to calculate the number of moles of HCl produced and hence the number of moles of ZCl4 present in the sample. Calculate the relative molecular mass, Mr, of ZCl4. From your answer deduce the relative atomic mass, Ar, of element Z and hence its identity.(9)

(b)

When copper reacts with dilute nitric acid, gaseous nitrogen monoxide is formed as shown by the following equation. 3Cu + 8HNO3 3Cu(NO3)2 + 4H2O + 2NO Calculate the volume of nitrogen monoxide, measured at 330 K and 98.0 kPa, which is formed when 1.25 g of copper metal reacts completely with an excess of dilute nitric acid.(6) (Total 15 marks)

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