Draw ‘dot-and-cross’ diagrams for these two acids, showing only outer shell electrons.
Suggest the bond angle values for HNC and NCO in isocyanic acid.
Suggest which acid, cyanic or isocyanic, has the shorter C-N bond length. Explain your response.
Isocyanic acid is a weak acid. $\text{HNCO} \rightleftharpoons \text{H}^+ + \text{NCO}^-$. $K_a = 1.2 \times 10^{-4}\ \text{mol dm}^{-3}$. Calculate the pH of a $0.10\ \text{mol dm}^{-3}$ solution of isocyanic acid.
Sodium cyanate, $\text{NaNCO}$, is used in the production of isocyanic acid. Sodium cyanate is made industrially by reacting urea, $(\text{NH}_2)_2\text{CO}$, with sodium carbonate. The other products formed in this reaction are carbon dioxide, ammonia and steam. Write an equation for the production of $\text{NaNCO}$ by this method.
Barium hydroxide, $\text{Ba(OH)}_2$, is fully ionised in aqueous solution. While $30.0\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ $\text{Ba(OH)}_2$ was added to $20.0\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ isocyanic acid, the pH was recorded. Calculate the $[\text{OH}^-]$ at the end of the addition.
Use your answer in (i) to calculate $[\text{H}^+]$ and the pH of the solution at the end of the addition.
On the axes below, sketch the way pH changes as a total of $30.0\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ $\text{Ba(OH)}_2$ is added to $20.0\,\text{cm}^3$ of $0.100\,\text{mol dm}^{-3}$ isocyanic acid.
The cyanate ion, $\text{NCO}^-$, can behave as a monodentate ligand. State what is meant by the terms monodentate and ligand.
Silver ions, $\text{Ag}^+$, react with cyanate ions to form a linear complex. Suggest the formula of this complex, including its charge.
When heated with $\text{HCl(aq)}$, organic isocyanates, RNCO, are hydrolysed to the amine salt, $\text{RNH}_3\text{Cl}$, and $\text{CO}_2$. $\text{RNCO} + \text{H}_2\text{O} + \text{HCl} \rightarrow \text{RNH}_3\text{Cl} + \text{CO}_2$ A $1.00\,\text{g}$ sample of an organic isocyanate, RNCO, was treated in this way, and the $\text{CO}_2$ produced was absorbed in an excess of aqueous $\text{Ba(OH)}_2$ according to the equation shown. $\text{Ba(OH)}_2(\text{aq}) + \text{CO}_2(\text{g}) \rightarrow \text{BaCO}_3(\text{s}) + \text{H}_2\text{O}(\text{l})$ The solid $\text{BaCO}_3$ precipitated weighed $1.66\,\text{g}$. Calculate the number of moles of $\text{BaCO}_3$ produced.
Hence calculate the $M_r$ of the organic isocyanate RNCO.
The R group in RNCO and $\text{RNH}_3\text{Cl}$ contains carbon and hydrogen only. Use your $M_r$ value calculated in (ii) to suggest the molecular formula of the organic isocyanate RNCO.
Suggest a possible structure of the amine RNH$_2$, which forms the amine salt, $\text{RNH}_3\text{Cl}$.
Suggest a possible structure of the amine RNH$_2$, which forms the amine salt, RNH$_3$Cl.