Question

The number of molecules in 32 g of methane is:

(a) 3.0x1023
(b) 12.04x1023
(c) 6.02x1023
(d) 2.4x1023​

Answer 1

Answer:-

12.04×10²³ molecules [Option.b]

Explanation:-

Given:-

→ Mass of Methane = 32g

To find:-

→ Number of molecules in 32g

of methane.

Solution:-

• Molar mass of Carbon (C) = 12g/mol

• Molar mass of Hydrogen (H) = 1g/mol

Hence, molar mass of Methane [CH₄] :-

= 12+ 1×4

= 16g/mol

Number of moles in 32g of Methane :-

= Given mass/Molar mass

= 32/16

= 2 moles

Hence, 2 moles are there.

Number of molecules :-

= No of moles × Avogadro Number

• Avogadro Number = 6.022×10²³

= 2×6.022×10²³

= 12.04×10²³ molecules

Thus, 12.04×10²³ molecules are there is 32g of methane.

Answer 2

Molar mass of Methane = 18 g.

[Methane = CH_4. Since C - atom = 12 u and H - atom = 1 u, so the mass of CH_4 is 18 u. Or, the molar mass of Methane = 18 g.]

Given mass = 32 g.

We know,

Number of molecules = Number of moles × N_A

And, Number of moles = (Given mass)/(Molar mass)

⇒No. of moles = 32 g ÷ 18 g = 2 mol

∴ Number of molecules = 2 × 6.022 × 10²³

⇒ Number of molecules = 12.044 × 10²³ {b}.