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saasta.ac.za National Science Olympiad Chemistry Paper : South African Agency for Science & Technology Advancement

Name of the Organization : SAASTA – South African Agency for Science & Technology Advancement
Announcement : National Science Olympiad
Year : 2016
Type : Past Papers
Subject : Chemistry

Website : http://www.saasta.ac.za/competitions/national-science-olympiad/
Download Question Paper :
Chemistry 2010 : https://www.southafricain.com/uploads/7272-2010-chemistry.pdf
Chemistry 2009 : https://www.southafricain.com/uploads/7272-2009-chemistry.pdf
Chemistry 2007 : https://www.southafricain.com/uploads/7272-chemistry_2007.pdf
Chemistry 2005/6 : https://www.southafricain.com/uploads/7272-chemistry2005-2006.pdf
Chemistry 2004/5 : https://www.southafricain.com/uploads/7272-chemistry_2005.pdf

National Science Olympiad Chemistry Paper

1. Freshly-prepared pancake batter (milk, flour and eggs) is always allowed to stand for some time before cooking to allow the batter to thicken. The reason the batter thickens is:

Related : SAASTA Grade 7- 9 Natural Science Olympiad Past Question Paper : www.southafricain.com/7265.html

A. water evaporates from the mixture
B. disulfide bonds form between proteins in the flour
C. unsaturated lipids in the egg become saturated
D. all of the above

2. The compound type formed by reacting a carboxylic acid with an alcohol, with loss of water is
A. an amide
B. an alkane
C. an ether
D. an ester

3. Which electronic configuration is most likely to give a stable -2 ion?
A. 1s22s22p6
B. 1s22s22p63s23p4
C. 1s22s22p63s23p64s2
D. none of the above

4. The reaction of calcium carbide (CaC2) with water involves the following steps
CaC2 (s) -> Ca2+ (aq) + C2 2- (aq) C2
2- (aq) + H2O -> C2H- (aq) + OH- (aq)
C2H- (aq) + H2O -> C2H2 (g) + OH- (aq)
Ca2+ (aq) + 2OH- (aq) ->Ca(OH)2 (s)

The overall reaction may be represented as :
A. CaC2 (s) + 2H2O -> Ca(OH)2 (s) + 2C (s)
B. C2H- (aq) + Ca2+ (aq) + 2OH- (aq) -> Ca(OH)2 (s) + C2H2 (g)
C. CaC2 (s) + 2H2O -> Ca(OH)2 (s) + C2H2 (g)
D. None of the above

5. Silver jewellery is usually made from an alloy of silver and copper. In order to check the silver content of a new batch of alloy, a jeweller dissolves 0.135 g of shaved alloy in 50.0 ml of concentrated HNO3 and then adds 1.00 M KCl solution until no more precipitate forms. After filtration and drying the AgCl precipitate is found to weigh 0.156 g. What is the percentage silver in the alloy?
[Hint – assume the AgCl precipitate is totally insoluble]
A. 75%
B. 100%
C. 50%
D. 90%

6. What is the maximum mass of adipic acid that can be prepared from 320 kg of cyclohexane and 300 kg of oxygen in the reaction shown below?
A. 1370 kg
B. 556 kg
C. 1389 kg
D. 548 kg

7. Which of the following processes is endothermic?
A. Addition of ammonium chloride to water
B. Neutralisation of an acid with a base
C. Addition of water to concentrated acid
D. Burning of magnesium metal in air to form magnesium oxide

8. Baking powder is used in baking to make cakes rise. Baking powder works in the following way
A. Baking powder is magnesium carbonate and it gives off carbonic acid when heated, causing rising.
B. Baking powder is a mixture of sodium bicarbonate and tartaric acid and these two react together giving off CO2 when water is added to cause rising.
C. Baking powder contains yeast, which releases CO2 on heating, causing rising.
D. None of the above

9. Metalloids are elements that show some properties of both metals and non-metals. Which of the following is an example of a metalloid?
A. potassium
B. bromine
C. silicon
D. plutonium

10. Emulsions are dispersions of one immiscible liquid in another. Everyday examples of emulsions include
A. Mayonnaise
B. Brine
C. Dishwashing liquid
D. Petrol

12. Which of the structures below are possible, keeping in mind the numbers of bonds that various atoms can form
CH3CH=CH2CH2CH3
CH3CH2SCH2CH3
CH3=CHCH2CH3
CH3CH=CHCH2Br
A. a and b
B. b and d
C. b and c
D. all of them

13. Metallic iron is produced in a blast furnace by smelting. This smelting process is best described as
A. Heating iron ore with an oxidising agent such as molecular oxygen
B. Heating iron ore with a reducing agent such as carbon
C. Heating iron ore until it melts
D. An electrolysis reaction

14. Carbon has two common allotropes graphite and diamond. Which of the following statements describing these allotropes is true?
a. Graphite conducts electricity because of a network of delocalised pi electrons, while diamond with only sigma bonds, does not.
b. Diamond is thermodynamically less stable than graphite at ordinary pressures.
c. Industrial grade diamonds are made more cheaply from graphite than they can be mined.
d. The density of diamond is greater than that of graphite.
A. a and b
B. b and c
C. d
D. all are true

15. In the reaction below, _____ is the reducing agent and _____ is the oxidising agent. _____ is reduced and _____ is oxidised.
2KCl + MnO2 + 2H2SO4 ®
K2SO4 + MnSO4 + Cl2 + 2H2O
A. KCl, H2SO4, Cl, Mn
B. KCl, MnO2, Mn, Cl
C. H2SO4, KCl, O2, Mn
D. MnSO4, K2SO4, Cl, Mn

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