S3 ChemistryTest 1

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!

1. (a) (i) Fermentation is the breaking down of sugars into and carbon dioxide in the presence of .
(ii) The raw materials from which alcohol may be prepared in our local areas are:-
- Ripe , , Maize, etc
(iii) Alcohol is prepared as follows:
- are covered in a pit to ripen.
- The bananas are put into a container and juice is using spear grass or banana leaves.
- The juice is to remove any solid particles and diluted.
- sorghum is added, the mixture covered and placed in a warm place for 2-3 days.


- Ground millet flour is mixed with water to form a .
- The is covered and left to stand in a warm place for 3 - 4 days then it is and roasted.
- The roasted paste is mixed with millet and water is added.
- The mixture is and left to stand in a warm place for 3 days.

The crude alcohol obtained is a mixture of water and alcohol; this mixture is fractionally distilled.
The alcohol is of boiling point; it comes off first as a . Water is the residue.

(b)When a sample of alcohol in a beaker was left standing in the Laboratory for several days the following is observed:

The level of the liquid because alcohol (ethanol) is .
(c) CH3CH2OH(l) + 3O2(g) ---------------------------------------à 2CO2(g) + 3H2O (l)

2. (a) Preparation of a dry sample of Carbon dioxide in the Laboratory Involves the following steps:

Dilute Hydrochloric acid is added to
The gas produced is passed through water to remove the and then through concentrated Sulphuric acid to .
Equation: CaCO3(s) 2HCl(aq) ----------------------------------------à CaCl2(aq) + H2O(l) + CO2(g)

(b) Preparation of a dry sample of Lead (II)Carbonate in the Laboratory involves:

- To Lead (II) nitrate solution add an aqueous sodium carbonate solution a little at a time
while .
- Filter off the or decant off the aqueous solution..
- Wash the precipitate with alittle distilled water and filter papers.

NaCO3 (aq) + Pb(NO3) 2(aq) + 2Na NO3(aq) + PbCO3(S)

(c) (i) The White powder turns when hot and when cold.

PbCO3(S) -------------------------------------> PbO(S) + CO2(g)

3. (a) (i) The atomic number of Carbon is 6 ( same as the number of protons)

(ii) The full symbol of Carbon, C-14 is 14 C
(b) (i) The use of Carbon atom, C14 in Archeology dating , finding the age of carbon containing articles.

(ii) The property of C14 which accounts for its use as stated in (b) (i) above is that its nucleus is unstable and so it .

(c) (i) C 2:4
(ii) Na 2:8:1
(iii) Cl 2:8:7

(d) The ions of sodium and chlorine are formed in the following way. Sodium its electron in order to become sodium ion.
Chlorine one electron to form a chloride ion.
In each case the ion formed is stable because it the electronic configuration of .

Carbon has four unpaired electrons in its while hydrogen has one electron in its outermost energy level. In order for carbon to acquire the noble gas electronic configuration of neon and helium respectively it its four electrons with the electron from four atoms of hydrogen to form .

(f) Properties of a Covalent bond: - Usually have melting points.
- Usually dissolve in solvents.
- Are , liquids or semi- solids at room temperature.
- Are made up of

4. (a) (i) Distinction between Polluted water and Hardened water:
Polluted water Is water that contains substances or forms of that alter its properties.
Hardened water is water that doesnot form with soap .

(ii) Permanent hard water is water that does not soften on heating / boiling and
Temporary hard water is water that softens on heating/boiling.

(b) (i) Water pollution; may be due to - Animal excreta, Oil, , soaps and detergents
(ii) Temporary hardness may be due to .

(iii) Permanent hardness may be due to .