The compound $\text{H}_3\text{PO}_4$ is prepared from phosphorus in two stages. Step 1: Phosphorus reacts with excess oxygen to give a white solid. Step 2: That white solid then reacts with water to produce $\text{H}_3\text{PO}_4$.
Write the equation for each stage. Step 1: ........................................ Step 2: ........................................
$\text{H}_3\text{PO}_4$ is a weak Brønsted-Lowry acid. Define the term weak Brønsted-Lowry acid.
$\text{H}_3\text{PO}_4$ is also produced in the process shown in reaction 1. Reaction 1: $\text{4H}_3\text{PO}_3 \rightarrow 3\text{H}_3\text{PO}_4 + \text{PH}_3$ Table 3.1 gives some relevant thermodynamic data.
Define the enthalpy change of formation.
Use the data in Table 3.1 to work out the enthalpy change, $\Delta H_r$, for reaction 1. $\Delta H_r = \ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ \text{kJ mol}^{-1}$
Explain why reaction 1 is a disproportionation reaction. Explain your answer with reference to the relevant oxidation numbers.
Fig. 3.1 shows a reaction scheme in which $\text{H}_3\text{PO}_4$ appears in several reactions.
Identify $A$, which reacts with propene in reaction 2 in the presence of $\text{H}_3\text{PO}_4$.
Draw the structure for $B$.
Name the reaction type in reaction 3.
Reaction 3 is followed using infrared spectroscopy. The O-H absorption frequency cannot be used to monitor the reaction. Use Table 3.2 to identify a suitable bond whose absorption frequency can be used to track the progress of reaction 3. State the change you would observe in the infrared spectrum during reaction 3. bond ………………………………………… change in infrared spectrum …………………………………………
Complete the equation to suggest the products formed when $\text{H}_3\text{PO}_4$ reacts with methanol, $\text{CH}_3\text{OH}$. $\text{H}_3\text{PO}_4 + 3\text{CH}_3\text{OH} \rightarrow \ldots$
Compound $T$ is a simple organophosphate. In the mass spectrum of $T$, the molecular ion peak is at $m/e = 182$. Its relative intensity is $12.7$. The $\text{M}+1$ peak has a relative intensity of $0.84$. Work out the number of carbon atoms in $T$. Hence suggest the molecular formula of $T$. Assume phosphorus and oxygen each have a single isotope. Show your working.