Question

1 g urea $(N{{H}_{2}}CON{{H}_{2}})$ , 1 g acetic acid $(C{{H}_{3}}COOH)$ and 1 g formaldehyde (HCHO) will have the hydrogen atom in the ratio:
A. 2:2:1
B. 1:1:2
C. 1:1:1
D. 1:2:1

Answer 1

Hint: We have to calculate the number of moles of all of the given compounds. After calculating the number of moles we can find the ratio of hydrogen atoms.

Complete step by step solution:
Number of moles of a compound is equal to the ratio of given weight of the element to the molar mass of the element. And the number of moles of the compound can also be calculated by the ratio of the number of particles to the Avogadro number of particles.
Given in the question:
Given mass of urea = 1g
Molecular formula of urea = $(N{{H}_{2}}CON{{H}_{2}})$
Molar mass of urea = 60 grams
Number of moles of urea = $\dfrac{1}{60}$ mole
Number of H atoms =$\dfrac{4{{N}_{0}}}{60}Hatom$
Given mass of acetic acid = 1g
Molecular formula of acetic acid = $(C{{H}_{3}}COOH)$
Molar mass of acetic acid= 60 grams
Number of moles of acetic acid= $\dfrac{1}{60}$ mole
Number of H atoms =$\dfrac{4{{N}_{0}}}{60}Hatom$
Given mass of formaldehyde= 1g
Molecular mass of formaldehyde= (HCHO)
Molar mass of formaldehyde = 30g
Number of moles of formaldehyde= $\dfrac{1}{30}$ mole
Number of H atoms =$\dfrac{2{{N}_{0}}}{30}=\dfrac{4{{N}_{0}}}{60}Hatom$
The ratio of hydrogen atoms will be 1:1:1.

Hence, the correct answer is option (C).

Note: Do not get confused with the formula to calculate the number of moles from molar mass and number of moles from number of particles. In the case where we calculate the number of moles from the number of particles we use Avogadro’s number and in the other case we use the molar mass.