Date Due: ………………………………………………………………..

Year 12

80%

A

70%

B

AS Level Chemistry

60%

C

2008 - 2009

50%

D

40%

E

Below

U

1.2

Assessed Homework

%

Amount of Substance

59

.

1. (a) Define the term relative atomic mass.

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(2)

(b) How would you calculate the mass of one mole of atoms from the mass of a single atom? ……………………………………………………………………………………. (1)

(c) Sodium hydride reacts with water according to the following equation.

NaH (s) + H2O (l) → NaOH (aq) + H2 (g)

A 1.00 g sample of sodium hydride was added to water and the resulting solution was diluted to a volume of exactly 250 cm3

(i) Calculate the concentration in moldm-3, of sodium hydroxide solution formed.

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(ii) Calculate the volume of hydrogen gas evolved, measured at 293 K and 100 kPa.

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(iii) Calculate the volume of 0.112 M hydrochloric acid which would react exactly with a 25.0 cm3 sample of sodium hydroxide solution.

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(8)

[TOTAL 11 marks]

2. (a) Sodium carbonate forms a number of hydrates of general formula Na2CO3.xH2O A 3.01 g sample of one of these hydrates was dissolved in water and the solution made up to 250 cm3.

In a titration, a 25.0 cm3 portion of this solution required 24.3 cm3 of 0.200 mol–1 dm–3 hydrochloric acid for complete reaction. The equation for this reaction is shown below.

Na2CO3 + 2HCl 2NaCl + H2O + CO2

(i) Calculate the number of moles of HCl in 24.3 cm3 of 0.200 mol dm–3 hydrochloric acid.

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(ii) Deduce the number of moles of Na2CO3 in 25.0 cm3 of the Na2CO3 solution.

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(iii) Hence deduce the number of moles of Na2CO3 in the original 250 cm3 of solution.

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(iv) Calculate the Mr of the hydrated sodium carbonate.

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(5)

(b) In an experiment, the Mr of a different hydrated sodium carbonate was found to be 250.

Use this value to calculate the number of molecules of water of crystallisation, x, in this hydrated sodium carbonate, Na2CO3.xH2O

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(3)

(c) A gas cylinder, of volume 5.00 × 10–3 m3, contains 325 g of argon gas.

(i) Give the ideal gas equation.

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(ii) Use the ideal gas equation to calculate the pressure of the argon gas in the cylinder at a temperature of 298 K.

(The gas constant R = 8.31 J K–1 mol–1)

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(4)

[Total 12 marks]

3. (a) A sample of ethanol vapour, C2H5OH (Mr = 46.0), was maintained at a pressure of

100 kPa and at a temperature of 366K.

(i) State the ideal gas equation.

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(ii) Use the ideal gas equation to calculate the volume, in cm3, that 1.36 g of ethanol vapour would occupy under these conditions.

(The gas constant R = 8.31 J K–1 mol–1)

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