Question

Iron reacts with dilute sulphuric acid according to equation, $Fe+{{H}_{2}}S{{O}_{4}}\to \text{ }FeS{{O}_{4}}+{{H}_{2}}$ , What mass of iron will react with $75c{{m}^{3}}$ of 0.5 M ${{H}_{2}}S{{O}_{4}}$ ?

Answer 1

A single-displacement reaction, also known as a single replacement reaction or an exchange reaction, occurs when one element in a molecule is replaced by another. It may be written as $\text{A}+\text{BC}\to \text{AC}+\text{B}$ , where A and B are distinct metals (or any other element that can form a cation, such as hydrogen) and C is an anion; or A and B are halogens and C is a cation.

Complete answer:
When Fe interacts with dilute ${{H}_{2}}S{{O}_{4}}$ , ferrous (II) sulphate is produced, which emits hydrogen gas.
$\Rightarrow Fe+{{H}_{2}}S{{O}_{4}}\to FeS{{O}_{4}}+{{H}_{2~}}$
Molar concentration is a measurement of a chemical species' concentration in a solution, specifically a solute's concentration, in terms of the amount of substance per unit volume of solution. The number of moles per litre, abbreviated as mol/L, is the most widely used unit for molarity in chemistry.
It is given as $c=\dfrac{n}{V}=\dfrac{N}{{{N}_{\text{A}}}V}=\dfrac{C}{{{N}_{\text{A}}}}$
$\Rightarrow C=\dfrac{n}{V}$
This can be interpreted as, $\mathrm{n}=\mathrm{C} \cdot \mathrm{V}$
$\Rightarrow \mathrm{n}(\mathrm{H}_2 \mathrm{SO}_4)=0.5 \cdot \dfrac{75}{1000} d m^{3}$
$\Rightarrow \mathrm{n}(\mathrm{H}_2 \mathrm{SO}_4)=0.0375 \mathrm{~mol}$
from the given chemical equation,
1 mole of Fe reacts with 1 mole of ${{H}_{2}}S{{O}_{4}}$ to get 1 mole of $FeS{{O}_{4}}$
$\therefore 0.0375 \mathrm{~mol}$ of ${{H}_{2}}S{{O}_{4}}$ will react with 0.0375 mole of $\mathrm{Fe}$
Also, $n(Fe)=\dfrac{m(\text{Fe})}{\text{M}(Fe)}$
$\Rightarrow \mathrm{M}(F e)=56 \mathrm{~g} / \mathrm{mol}$
$\Rightarrow \mathrm{m}(F e)=\mathrm{n}(F e) \cdot \mathrm{M}(F e)$
$\Rightarrow \mathrm{m}(\boldsymbol{F e})=0.0375 \cdot 56$
$\Rightarrow \mathrm{m}(\mathrm{Fe})=2.10 \mathrm{grams}$
Hence 2.10 grams is the correct answer.

Note:
The use of molar concentration in thermodynamics is frequently inconvenient since the volume of most solutions varies somewhat with temperature owing to thermal expansion. This difficulty is typically handled by utilising temperature adjustment factors or a temperature-independent concentration measure such as molality. The reciprocal amount denotes the dilution (volume) that may be found in Ostwald's dilution law.