Electron-Pair Sharing Reactions · Paper 1 — Free Chemistry HL Practice Questions

When ammonia reacts with a hydrogen ion to form the ammonium ion, $\text{NH}_3 + \text{H}^+ \rightarrow \text{NH}_4^+$, which statement correctly describes the bond formed and the formal charge on nitrogen in $\text{NH}_4^+$?

A hydride ion, $\text{H}^-$, donates its lone pair to boron trifluoride, $\text{BF}_3$, forming the tetrahydridoborate ion, $\text{BH}_4^-$. What is the change in hybridisation of the boron atom and the molecular geometry of the species as $\text{BF}_3$ becomes $\text{BH}_4^-$?

In the complex ion $[\text{Cu(NH}_3)_4]^{2+}$, which statement correctly describes the Cu–N bond and identifies the Lewis acid in this interaction?

Boron trifluoride, $\text{BF}_3$, reacts with diethyl ether, $(\text{C}_2\text{H}_5)_2\text{O}$, to form a stable adduct in which the oxygen atom donates a lone pair to the boron atom. Which change in hybridisation of the boron atom occurs when this adduct forms?