Calculate the pH for $0.10\ \text{mol dm}^{-3}$ $\text{HCN}(aq)$.
Draw a ‘dot-and-cross’ diagram to show the bonding in the hydrogen cyanide molecule. Include only the outer shell electrons.
State the hybridisation of the carbon and nitrogen atoms in hydrogen cyanide, and state the H-C-N bond angle.
Suggest structures for the organic products $A$ and $B$ in the reactions below. Assume that $\text{HCN}$ reacts in the same way as $\text{RCN}$.
If a measured amount of $\text{KCN}$ is added to a solution of $\text{NiCl}_2$, the complex $[\text{Ni(CN)}_2\text{Cl}_2]^x$ is formed. Deduce the overall charge, $x$, on this complex.
The complex can form two distinct isomers with the same geometry (shape) around the nickel ion. State the type of isomerism shown by these isomers.
If bromide ions are present in the solution, the complex $[\text{Ni(CN)}_2\text{ClBr}]^x$ can form. Assuming that $[\text{Ni(CN)}_2\text{ClBr}]^x$ has the same geometry as $[\text{Ni(CN)}_2\text{Cl}_2]^x$, state how many isomers of $[\text{Ni(CN)}_2\text{ClBr}]^x$ could exist, and draw their structures.
Aqueous $\text{KCN}$ is added little by little to a solution of $\text{NiSO}_4$ until $\text{KCN}$ is in excess. The following series of reactions takes place: $\text{NiSO}_4 \xrightarrow{\text{KCN}} C \xrightarrow{\text{more KCN}} D \xrightarrow{\text{KCN in excess}} E$ Green precipitate $\rightarrow$ yellow solution $\rightarrow$ red solution The oxidation state of nickel does not change during these reactions. None of $C$, $D$ or $E$ contains sulfur. $C$ contains no potassium. The K:Ni ratio in $D$ is $2{:}1$. The K:Ni ratio in $E$ is $3{:}1$. Use the information to suggest the formulae of $C$, $D$ and $E$.