Question

Dinitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation:
${{N}_{2}}(g)+3{{H}_{2}}(g)\to 2N{{H}_{3}}(g)$
(i) Calculate the mass of ammonia produced if 2.00 $\times$ ${{10}^{3}}$ g dinitrogen reacts with 1.00 $\times$ ${{10}^{3}}$ g of dihydrogen.
(ii) Will any of the two reactants remain unreacted?
(iii) If yes, which one and what would be its mass?

Answer 1

Hint The chemical reaction of any two compounds to form a third compound is a spontaneous process in nature. Within the reactants, one can be limited and other can be in excess depending upon the stoichiometry of the reaction and reaction conditions.

Complete step by step solution:
Let us start by knowing the basics of chemical reaction taking place in nature knowingly and unknowingly.
Chemical reaction- A chemical reaction is a process in which substances act mutually on each other to bring about the chemical transformation to other substances.
Balancing of chemical reaction- The balancing of chemical reactions is a vital and prior step while calculating anything related to the given reactions.
Proper balancing gives specific stoichiometric coefficients which helps further in mass and energy balances.
Remember that, the phenomenon of conservation of mass takes place within the reaction i.e.
Mass of reactants = Mass of products
Limiting reactant- The limiting reactant is the reactant which is totally consumed when the chemical reaction takes place. This is the reactant that controls the amount of formation of the product. The reaction will stop when the limiting reactant is consumed completely.
Excess reactant- The reactant which remains after specific consumption with the limited reactant is known as excess reactant. The excess reactant remains as there is nothing left in the reactant streams so that it will be used to form further any product.
Illustration- Given that,
(i)Dinitrogen reacts with dihydrogen to give ammonia as a product.
Stoichiometrically looking towards the given equation we can analyse the above statement as-
One mole of dinitrogen in gaseous form reacts with three moles of gaseous dihydrogen atoms to give two moles of gaseous ammonia.
Data-
Mass of dinitrogen reacts = 2.00 $\times$ ${{10}^{3}}$ g
Mass of dihydrogen reacts = 1.00 $\times$ ${{10}^{3}}$ g
The mass of ammonia produced can be calculated as follows-
The reaction is,
${{N}_{2}}(g)+3{{H}_{2}}(g)\to 2N{{H}_{3}}(g)$
which clearly tells us that
1 mole of dinitrogen $\equiv$ 3 moles of dihydrogen $\equiv$ 2 moles of ammonia
i.e. 28 g of dinitrogen $\equiv$ 6 g of dihydrogen $\equiv$ 34 g of ammonia
Thus, it states that
28 g of dinitrogen requires 6 g of dihydrogen to produce 34 g of ammonia
Now, according to given data-
2.00 $\times$ ${{10}^{3}}$ g of dinitrogen will produce = ($\dfrac{34}{28}$) $\times$2.00 $\times$ ${{10}^{3}}$ g = 2430 g of ammonia
Hence, ammonia produced = 2430 g.
(ii)By looking towards the reaction mechanism and stoichiometry we can say that, dihydrogen will remain unreacted to some extent as it is present in excess amounts.
(iii)The amount of hydrogen that remains unreacted can be calculated by using stoichiometric coefficients as,
28 g of dinitrogen requires 6 g of dihydrogen to produce 34 g of ammonia
2.00 $\times$ ${{10}^{3}}$g of dinitrogen will require = ($\dfrac{6}{28}$) $\times$2.00 $\times$ ${{10}^{3}}$g = 428.5 g of dihydrogen
Thus,
Amount of hydrogen that remains unreacted = (1.00 $\times$ ${{10}^{3}}$)– 428.5 g = 571.5 g

Hence, unreacted hydrogen = 571.5 g.

Note: Do note that, before calculating for any unspecified quantity for a given problem; remember to balance the equation at first then proceed in a further direction.
Dinitrogen is the dimer of nitrogen molecules. Similarly, dihydrogen is the dimer of hydrogen. So, writing its basic form or its dimer form in the solution won’t make much difference.
Check the units.