Use this ZIMSEC O-Level Chemistry Paper 2 November 2014 marking scheme for checking answers, revision, and exam preparation in Zimbabwe.
A free account is needed to download. Sign in or create one
This is the ZIMSEC O-Level Chemistry marking scheme for Paper 2 from November 2014. It shows how marks are awarded, so you can mark your own answers. The paper code is 4189/2.
\[
4189 / 2
\]
1 (a) $\mathrm{Kp}=\frac{\mathrm{P}_{\mathrm{NH} 3}^{2}}{\mathrm{P}_{\mathrm{H}_{2}}^{3} \cdot \mathrm{PN}_{2}}$;
Deject[J]
(A)
()
[1]
(b) $\underset{2}{\mathrm{~N}_{2}}+\underset{2}{3 \mathrm{H}_{2}} \longleftrightarrow \underset{0}{2 \mathrm{NH}_{3}}$
$2-x 2-3 x \quad 2 x$
$x=0.2$
made on arroves.
at equilibrium moles of $\mathrm{N}_{2}=1.8$ mols;
[1]
moles of $\mathrm{H}_{2}=1.4$ moles;
[1]
moles of $\mathrm{NH}_{3}=0.4$ moles;
[1]
(c) $\quad \mathrm{P}_{\mathrm{N} 2}=\frac{1.8}{3.6} \mathrm{P}_{\mathrm{T}}$
(安) (i) ecf for b.
01
$\mathrm{PN}_{\mathrm{H} 3}=\frac{0.4}{3.6} \mathrm{P}_{\mathrm{T}} ;$
$P_{H 2}=\frac{1.4}{3.6} P_{T}$
ech from b.
$\omega$
$\mathrm{Kp}=\frac{\mathrm{P}_{\mathrm{NH}_{3}}^{2}}{\mathrm{P}_{\mathrm{N} 2} \cdot \mathrm{P}_{\mathrm{H}_{2}}^{3}}$
田
$=\left(\frac{0.4}{3.6 \mathrm{p}_{\mathrm{T}}}\right)\left(\frac{1.4}{3.6 \mathrm{p}_{\mathrm{T}}}\right)^{3}\left(\frac{1.8}{3.6 \mathrm{p}_{\mathrm{T}}}\right) ;$
$40.7=\frac{0.16}{\mathrm{P}_{\mathrm{T}}{ }^{2}} ;$
* $\mathrm{P}_{\mathrm{T}}=0.063 \mathrm{~atm} ; \quad 4,2 \quad 0,102$ atm
[1]
2
(a) The potential difference (or emf) of half cell measured relative to a standard hydrogen electrode;
(ii) accen
(b) (i) temperature of 298 K ;
(A) $25^{\circ} \mathrm{C}$
[1]
[1]
pressure of latms.
[1]
solutions with concentrations of $1.0 \mathrm{~mol} / \mathrm{dm}^{3}$;
[1]