science(chemistry) sa practice

8/2/2019 Science(Chemistry) SA practice

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Secondary 4 Semestral Assessment Practice

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3. Ammonia gas is produced when a little sodium hydroxide and a few pieces of

aluminium foil are added to an unknown solution. The solution may contain

A sodium nitrate

B zinc chloride

C copper(II) sulfate

D an acid

4. Sulfur dioxide has a low boiling point. This is because

A covalent bonds in the molecule are easily overcome

B ionic bonds are broken in the molecule

C weak intermolecular forces of attraction are easily overcome

D sulfur dioxide molecule contains two S=O bonds in it

5. A white precipitate which is insoluble in excess aqueous ammonia is produced when

aqueous ammonia is added to an unknown solution. The unknown solution may be

A zinc nitrate

B lead(II) nitrate

C sodium chloride

D sodium sulfate

6. Predict whether potassium sulfate has ionic, covalent or metallic bonding and

whether the compound has a low or high melting point.

Answer:


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7. When solid calcium carbonate is heated, it decomposes to form calcium oxide andcarbon dioxide.

(a) Construct a balanced equation, with state symbols, for the above reaction.(b) In an experiment, 1 mole of calcium carbonate was heated to form carbon

dioxide and calcium oxide. Calculate the mass of carbon dioxide formed.

8. Ammonium nitrate is dissolved into water. The temperature fell by 5.2oC.

(a) Write down the ions that ammonium nitrate forms in solution.(b) With reference to energy changes, what reaction is this known as?

9. Given the equation : 4FeO Fe + Fe3O4, calculate the oxidation numbers of iron inall the reactant and the products.

10. One important industrial use of sulfuric acid is in the manufacture of aluminiumsulfate which is used in water purification.

(a) Write down the two reagents that can be used to produce aluminium sulfate.(b) Another aluminium compound, aluminium oxide, can be used to extract purealuminium. With reference to the position of aluminium in the metal reactivity series,state how do you extract pure aluminium from an aluminium oxide ore.

11. Scientists study Period 3 elements and investigate the properties of the elements and

their compounds. One of the Period 3 elements is sodium. Metals are known to be goodconductors of electricity.

(a) Name the Period 3 elements which are good conductors of electricity.(b) An element Y, in Period 3, burns in air on gentle heating to produce a colourless

gas with the formula YO2. This gas is known to cause acid rain. Identify theelement Y.

(c) Which unreactive element in Period 3 can be used to fill an inert atmosphere inlight bulbs?

Hi, you may e-mail to me your answers, and I can give you comments about your answers.My e-mail [email protected]

Mr Chong
mailto:[email protected]:[email protected]:[email protected]:[email protected]

science(chemistry) sa practice

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