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6 Nitrobenzene, C6H5NO2, can be reduced to phenylamine, C6H5NH2, in acid solution in a two step process - CIE - A-Level Chemistry - Question 6 - 2016 - Paper 1
Question 6
6 Nitrobenzene, C6H5NO2, can be reduced to phenylamine, C6H5NH2, in acid solution in a two step process. (a) (i) Balance the half-equation for this reaction to work... show full transcript
Worked Solution & Example Answer:6 Nitrobenzene, C6H5NO2, can be reduced to phenylamine, C6H5NH2, in acid solution in a two step process - CIE - A-Level Chemistry - Question 6 - 2016 - Paper 1
Step 1
(a) (i) Balance the half-equation for this reaction to work out how many moles of electrons are needed to reduce one mole of nitrobenzene.
Answer
To balance the half-equation, we start with the reduction of nitrobenzene. The equation is:
This shows that for the reduction of one mole of nitrobenzene, 6 moles of electrons are required.
Step 2
(a) (ii) Use oxidation numbers or electrons transferred to balance this equation.
Answer
For the overall reaction represented as:
To balance it, we observe the oxidation states of each component. The oxidation state of Sn changes, indicating it is being oxidized, while the nitrogen in nitrobenzene is being reduced.
Step 3
(b) Calculate the percentage yield.
Answer
To calculate the percentage yield, we first find the theoretical yield of phenylammonium chloride based on the molar mass of nitrobenzene.
Molar mass of C6H5NO2 = 123 g/mol
Theoretical yield = (5.0 g / 123 g/mol) * 129.5 g/mol = 5.26 g
Then the percentage yield is given by:
Step 4
(c) (i) Calculate the mass of phenylamine, C6H5NH2, produced when 4.2g of phenylammonium chloride reacts with an excess of NaOH(aq).
Answer
The molar mass of phenylammonium chloride (C6H5NH3Cl) is 127 g/mol, thus:
Moles of phenylammonium chloride = ( \frac{4.2}{127} \approx 0.0331 , ext{mol} )
Since the reaction produces phenylamine in a 1:1 ratio, the mass of phenylamine produced:
Step 5
(d) How does the basicity of phenylamine compare to that of ethylamine? Explain your answer.
Answer
Phenylamine is less basic than ethylamine because in phenylamine, the lone pair of electrons on the nitrogen is delocalized into the aromatic system. This delocalization makes the lone pair less available for protonation, thus reducing the basicity. Ethylamine, on the other hand, has its lone pair available for a proton to bond, making it a stronger base.