Question

90g mixture of ${H_2}$ and ${O_2}$ is taken in stoichiometric ratio and gives${H_2}O$ with 50% yield. The produced mass of ${H_2}O$ (in gm) is:
A. 45 g
B. 36 g
C. 20 g
D. 90 g

Answer 1

Hint: Stoichiometry is used to determine the number of products and reactants that are produced in a reaction. It is developed by the concept of law of conservation of mass, law of definite proportion and law of multiple proportion .

Complete step by step answer:
Now according to Avogadro’s law we know that one mole molecules of all gases contain equal numbers of gases. We will apply this concept to a wider view in this question. It is an example of gravimetric analysis where we relate the weights of two substances with the weight of the substance in the product. The equation to the process occurring in the question is:

 $2{H_2} + {O_2} \to 2{H_2}O$
According to this equation
2(1X2) g of hydrogen combines with (16x2) g of oxygen to give 2(2+16) g of water.
Hence we can say 4g of Hydrogen and 32g of oxygen gives 36 g of water. If the 90g mixture of hydrogen and oxygen gives 50% yield then the produced mass of ${H_2}O$in grams will be
90 g mixture yields 50% of ${H_2}O$

$\dfrac{{36 \times 90}}{{36}} = 90$g
Since 90 g of mixture gives 50% by mass yield of product, the mass of ${H_2}O$ produced would be 45g which can be concluded from the explanation above.

Hence the correct option is option A.

Note:
Since 90g mixture gives 50% by mass yield of product. The mass of ${H_2}O$ produced would directly become 45g. Solving the questions on stoichiometry always keeps in mind the molar proportion of the equation and always writes a balanced equation to the process.