Page 135 - Chemistry

11. Study the information in the following table and answer the questions that follow. The letters
do not represent the actual chemical symbols of the elements.
ELEMENT U V W X Y Z
NUMBER OF PROTONS 18 20 6 16 19 17
NUMBER OF NEUTRONS 22 20 8 16 20 20
Which of the above elements are:
(i) Likely to be radioactive?
(ii) Able to form a compound with the highest ionic character?

12. The isotope decays by Beta,  -emission to a stable nuclide. The half-life of the
24
isotope is 15hours 2.0g of is allowed to decay. Determine the mass of left after 90hours
11
13. (a) Complete the following nuclear equation
55 55

Cr Mn + ____________
24 25
(b) 100g of a radioactive substance was reduced to 12.5g within 15.6 years. Determine
the half-life of the substance

SECTION III PRATICALS

KAKAMEGA CENTRAL DISTRICT
CONFIDENTIAL
ACCESS TO:-
 1M NaOH
 1M NH 4OH
 1M HCL
 0.01m PB (NO 3) 2
 Source of heat
 pH chart (PH=1 to 14)
 10ml of solution K
 Sodium hydrogen carbonate

PREPARATION OF SOLUTIONS:
1. Solution J
3
3
Dissolve 17g of ammonium iron (II) sulphate in 50cm of 2M H 2SO 4 dilute to 1dm
2. Solution K KMnO 4
3
3
Dissolve 1.6g of potassium manganate vii in 20cm of 2 MH 2SO 4 dilute to 1dm
3. Solution R
3
Dissolve 40g of sodium thiosulphate in 1dm of solution
4. Solution S
3
3
Dissolve 172cm of concentrated hydrochloric acid in 1dm of solution
5. Solid Y is aluminium sulphate
6. Solid Z is oxalic acid.

Each candidate will require:
Q1.
3
1. Solution J - 100cm
2. Burette
3
3. Solution K- 100cm
4. Pipette
5. 2 conical flasks

www.kcse-online.info 134