Question $9(1$ point$)$

What is the oxidation number of chromium in $K_{2}C{r}_2{O}_7?$

$+4$

$+2$

$+3$

$+6$

$+5$

Question $10(3$ points$)$

For the following question, you need to show all of your work to get full marks.

$P{b}_{(aq)}^{2+}+2e^{-}P{b}_{(s)},E_r^0=-0\mathrm{.}13V$

$S{c}_{(aq)}^{3+}+3e^{-}S{c}_{(s)},E_r^0=-2\mathrm{.}02V$

a$)$ Write a balanced chemical equation for a spontaneous reaction involving these

half reactions. Need to show how this equation was obtained in order to get full

marks.

b$)$ Explain your rationale for the reaction going in this direction using calculations.