Question

The combustion of hydrogen-oxygen mixture is used to produce water at very high temperature ($ \approx {2500^ \circ }C$) needed for certain types of welding operations:
${{\text{H}}_{\text{2}}}{\text{ + }}\dfrac{{\text{1}}}{{\text{2}}}{{\text{O}}_{\text{2}}} \to {{\text{H}}_{\text{2}}}{\text{O; }}\Delta {\text{H = - 241}}{\text{.8KJ}}$
Quantity of heat (in KJ) evolved when a $180g$ mixture containing equal parts of ${H_2}$ and ${O_2}$ mass burned, is:
A.$ - 2.72 \times {10^3}KJ$
B.$ - 6.80 \times {10^2}KJ$
C.$ - 1.36 \times {10^3}KJ$
D.$ - 4.3524 \times {10^4}KJ$

Answer 1

Hint: Combustion: It is defined as the process of burning in air. Combustion of hydrogen-oxygen means hydrogen is burning in air which yields water. The temperature required is high for the reaction.

Complete step by step answer:
Let us talk about reagents, products, limiting reagent, excess reagent and combustion.
Combustion: It is defined as the process of burning in air. Combustion of hydrogen-oxygen means hydrogen is burning in air which yields water. The temperature required is high for the reaction.
Reagents: those compounds which react with each other to form the other compounds, are known as reagents. They are present on the left side of the reaction.
Products: The compounds formed by the reaction of reagents, are known as products. They are present on the right side of the reaction.
Limiting reagent: The reagent which is completely consumed during the reaction, is known as limiting reagent.
Excess reagent: The reagent which is left after the reaction, is known as excess reagent.
Balanced reaction: The reaction in which the number of all atoms on both sides i.e. on the reactant side and on the product side are same, are known as balanced reactions.
Here in the question we are given the mass of mixture as $180g$. The mixture contains hydrogen and oxygen in equal quantity so the mass of both of these will be $90g$ each. Now from the given balanced reaction we can see that one mole of hydrogen reacts with half mole oxygen to form one mole of water. ${{\text{H}}_{\text{2}}}{\text{ + }}\dfrac{{\text{1}}}{{\text{2}}}{{\text{O}}_{\text{2}}} \to {{\text{H}}_{\text{2}}}{\text{O; }}\Delta {\text{H = - 241}}{\text{.8KJ}}$. And the heat produced is $ - 241.8KJ$. Here if we see then we will get oxygen as a limiting reagent.
As $16g$ i.e. one mole of oxygen produce $ - 241.8KJ$ of heat then $90g$ of oxygen will produce $\dfrac{{ - 241.8}}{{16}} \times 90 = - 1360KJ$. Hence option C i.e. $ - 1.360 \times {10^3}$ or $ - 1360KJ$ is correct.

Hence option C is correct.

Note:
Welding is the process which is used to join the metals. In the welding process generally first the metals are heated at high temperature and metal melt due to high temperature and then let them cool.