Question

1.204 * 10^24 molecules are present in a sample of methane. What will be its weight (in grams)?
(A) 32
(B) 24
(C) 16
(D) 12​

Answer 1

Answer:-

Weight of the sample is 32 grams .

Explanation:-

Here, we are given with the number of molecules present in a sample of methane [CH₄] and we have to calculate the mass/weight of the sample.

Number of moles in the sample :-

= No of molecules/Avogadro Number

= 1.204×10²⁴/6.022×10²³

= 12.04/6.022

= 1.99 ≈ 2 moles

________________________________

• Molar mass of Carbon (C) = 12 g/mol

• Molar mass of Hydrogen (H) = 1 g/mol

Hence, molar mass of methane :-

= 12 + 1×4

= 16 g/mol

Now, we know that :-

Mass = No of moles × Molar mass

⇒ Mass = 2 × 16

⇒ Mass = 32 g

Thus, correct option is (A)!

Answer 2

Number of molecules = 1.204 × 10²⁴

Mass = (Molar Mass)(No. of moles)

⇒ Mass = (16 g)(No. of molecules ÷ Avogadro constant)

⇒ Mass = (16 g)(1.204 × 10²⁴ ÷ 6.022 × 10²³)

⇒ Mass = (16)(0.199 × 10)

⇒ Mass = (16 g)(2)

⇒ Mass = 32 g.

∴ The weight in grams is 32 (A).