Question 1
State two laboratory rules that should be followed to avoid contamination and wastage of chemicals
Answer
- Label all the chemicals to avoid confusion.
- Always use a clean spatula/dropper for scooping/droping substance from container
- Always use a clean spatula/dropper for scooping/droping substance from container
Question 2
Describe one method used to distinguish between sodium sulphate and sodium sulphite
Answer
Add acidified barium chloride /nitrate,a white precipitate will be formed with sodium sulphate and no white precipitate with sodium sulphite
Question 3
A gaseous compound consists of 86% carbon and 14% hydrogen by mass. At s.t.p 3.2 dm3 of the compound has a mass of 6 grams. Calculate:
a) its empirical formulae ( C=12,H=1, MGV=at stp 22.4dm3)
b) its molecular formulae
Answer
a)
E.F = CH2
b)
E.F = CH2
b)
Question 4
The graph below shows amount of calcium carbonate and calcium chloride varying with time in the reaction
a) Which curve shows amount of calcium chloride varying with time
b) Explain why the two curves become horizontal after given period of time
c) Sketch on graph curve II would appear if the experiment was repeated using more dilute hydrochloric acid solution
Answer
a) CURVE II
b) The reaction will have reached completion and the amount of reactants and products do no change further
c)
b) The reaction will have reached completion and the amount of reactants and products do no change further
c)
Question 5
The thermal chemical equation for the reaction between X and Y are shown below.
a) Other than change in temperature, suggest two ways in which yield of X2Y can be increased
b) draw a well labeled energy level diagram for the forward reaction
Answer
a)
- Increasing the pressure
- Decreasing the temperature
b)
- Decreasing the temperature
b)