2abche acids bases stoichiometry test answers

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Page 1: 2ABCHE Acids Bases Stoichiometry TEST ANSWERS

TEACHER DEVELOPMENT CENTRE CHEMISTRY

YEAR 11 CHEMISTRY 2BCHE

TEST 4

Acids and Basesand Stoichiometry

Recommended time: 1 hour

ANSWERS

PLEASE DO NOT TURN THE PAGE UNTIL INSTRUCTED TO DO SO

© Department of Education and Training – Teacher Development Centre – Chemistry – L. Taylor - 2008

Page 2: 2ABCHE Acids Bases Stoichiometry TEST ANSWERS

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YEAR 11 CHEMISTRY TEST

ANSWER BOOKLET

NAME : DATE :

MULTIPLE CHOICE ANSWER SHEET

1. [A] [B] [C] [D]

2. [A] [B] [C] [D]

3. [A] [B] [C] [D]

4. [A] [B] [C] [D]

5. [A] [B] [C] [D]

6. [A] [B] [C] [D]

7. [A] [B] [C] [D]

8. [A] [B] [C] [D]

9. [A] [B] [C] [D]

10. [A] [B] [C] [D]

© Department of Education and Training – Teacher Development Centre – Chemistry – L. Taylor - 2008

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11. [A] [B] [C] [D]

12. [A] [B] [C] [D]

13. [A] [B] [C] [D]

14. [A] [B] [C] [D]

15. [A] [B] [C] [D]

16. [A] [B] [C] [D]

17. [A] [B] [C] [D]

18. [A] [B] [C] [D]

Page 3: 2ABCHE Acids Bases Stoichiometry TEST ANSWERS

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CHEMISTRY 11 Contd

WRITTEN SECTION (17 marks)

1. Write Balanced IONIC equations for the reactions between each of the following:

a) Solid zinc oxide and hydrochloric acid.

ZnO(s) + 2H+(aq) → Zn2+(aq) + H2O(l)

b) Sodium carbonate solution and sulfuric acid.

CO32- (aq) + 2H+(aq) → H2O(l) + CO2(g)

c) Magnesium hydroxide solution and nitric acid.

H+(aq) + OH¯(aq) → H2O(l)

(3 marks)

2. An unknown organic compound was found to contain 49.5% carbon, 5.1% hydrogen, 28.9% nitrogen and the remainder oxygen. Calculate the empirical formula of this unknown compound. (3 marks)

C H N O

49.5 5.1 28.9 16.5 12 1 14 16

= 4.125 = 5.1 = 2.06 = 1.03

4 4.95 2 1 (Dividing by 1.03)

Answer: C4H5N2O

© Department of Education and Training – Teacher Development Centre – Chemistry – L. Taylor - 2008

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Page 4: 2ABCHE Acids Bases Stoichiometry TEST ANSWERS

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3. A sample of hydrated copper sulfate, CuSO4.xH2O (where x represents an unknown amount of water), is blue, however, the anhydrous form (CuSO4) is white. A 28.7g sample of hydrated copper sulfate was heated and found to weigh 17.45g after being fully dehydrated by heating.

(a) Calculate the percentage by mass of water in the original hydrated sample.(1 mark)

Percentage of water = 28.7 – 17.45 = 5.14% 28.7

(b) Find the number of moles of water and CuSO4 in the hydrated sample.(2 marks)

Moles CuSO4 = 17.45/139.5 = 0.125 mol

Moles water = 11.25/18 = 0.625 mol

(c) From your answers in (b) find the value of ‘x’ in the hydrated sample and thus determine its empirical formula. (2 marks)

Ratio: 0.625/0.125 = 5 : 1

Hence: CuSO4.5H2O

4. One mole of a substance with the empirical formula CH2O is found to have a mass of 60g. Determine the substance’s molecular formula.

1 mole CH2O weighs 30g

Sample weighs 60g, hence molecular formula is C2H4O2

(2 marks)

5. The overall reaction for the production of Aluminium is:3C(s) + 2Al2O3(l) → 4Al(l) + 3CO2(g)Calculate the mass of Aluminium produced from the reaction of 1.50 tonnes of carbon and 2.50 tonnes of 2Al2O3.

Moles C = 3500/12.01 = 124.9 mol, requires 83.26 mol Al2O3

Moles Al2O3 = 10500/101.96 = 102.98 mol, requires 154.4 mol CLimiting reagent is CMoles of Al produced = 4/3(124.9) = 166.5 molMass Al = 166.5 x 26.98 = 4493g = 4.49 tonnes. (4 marks)

TOTAL: 35 marks.

© Department of Education and Training – Teacher Development Centre – Chemistry – L. Taylor - 2008

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