(a)[2]
Write an equation that shows the standard enthalpy change of formation of $\text{H}_2\text{O}$. Include state symbols.
(b)[2]
Water is one of the products when $\text{B}_2\text{O}_3$ reacts with $\text{NH}_3$, as shown in reaction 2: $\text{B}_2\text{O}_3 + 2\text{NH}_3 \rightarrow 2\text{BN} + 3\text{H}_2\text{O}$. Table 3.1 gives the standard enthalpy change of formation, $\Delta H_f^\circ$, for some substances. Use the information in Table 3.1 to calculate the enthalpy change, $\Delta H$, for reaction 2.
(c(i))[1]
Suggest the structure and bonding present in boron carbide.
(c(ii))[2]
In $100$ g of pure boron carbide, $78.26$ g is boron. Calculate the empirical formula of boron carbide. Show your working.