Describe how the oxides of tin and lead in the $+4$ oxidation states differ in their behaviour on heating.
A sample of liquid $\text{PbCl}_4$ is put into a flask and the flask is gently warmed. A gas is given off and a white solid forms. When the gas is bubbled through $\text{KI}(aq)$, purple fumes appear. Explain these observations using data from the Data Booklet where suitable, and write equations for all reactions.
If the same experiment is repeated with liquid $\text{SnCl}_4$ instead of $\text{PbCl}_4$, no gas is evolved and there is no reaction with $\text{KI}(aq)$. Explain.
The molecule dichlorocarbene, $\text{CCl}_2$, can form under certain conditions. It is highly unstable and reacts with water to make carbon monoxide and a strongly acidic solution. Suggest the electron arrangement in $\text{CCl}_2$ and draw a dot-and-cross diagram to show it. Predict the shape of the molecule.
Write an equation for the reaction between $\text{CCl}_2$ and water.