Page 292 - Chemistry

KISUMU DISTRICT

1.
1 2 3
Final burette reading (cm )
3
Initial burette reading (cm )
3
Vol. of sol. C used (cm ) 22.9 22.9 22.9
3

. (i) C. T
(ii) D.P ½ mk
(iii) Ac 1mk
(iv) AV 1mk
(v) F ½ mk
(a) (i) Average volume of B (above
(ii) Moles of NaOH solution C = 25 x 0.4 = 0.01
1000
(iii) Moles of HCl solution B
NaOH + HCl H 2O + NaCl
Ratio base : acid = 1: 1
HCl = 0.01

(ii) Molarity of HCl
= 0.01 x 1000 = ans, (a(iv)
Ans (a) (i)
Table 1
(b) (i) 1.2 + 12 + 12 = 12 (above)
3
(c) (ii) Moles of NaOH solution C
Ans (b) (i) x 0.4 = ans b(ii)
1000
3
iii) Calculate the number of moles of hydrochloric acid in 200cm solution D
NaOH (aq) + HCl (aq) NaCl +H 2O
Mole ratio Acid: base = 1:1
In 25.0cm solution of HCl = Ans b(ii)
3
Moles of hydrochloric acid solution B contained in 25.0cm of B
200 x ans (ii) = ans (iii)
25
iv) Moles o hydrochloric acid solution B contained in 25.0cm3 of B= 25 x ans a(iv)
1000
= ans. (b)(iv)
v) Moles of HCl that reacted with Calcium Carbonate
= ans (b) (iv) – ans (b)(iii) ( ½ mk)
CaCO 3 + 2HCl CaCl 2 + CO 2 + H 2O
Mole ratio Carbonate: acid = 2:1 ½mk
Mole of calcium carbonate = ans.(b)(iv) – ans. (b) (iii) ( ½ mk)
2 = ans. (b)(v)
(vi) RMM = 100g
Mass in mixture = 100 x ans (b) (v) ½

www.kcse-online.info 291