Question

If 3.01 × 10²⁰ molecules are removed from 98 mg H₂SO₄ then find out mass of oxygen in the H₂SO₄ left behind.
यदि 98 mg H₂SO₄ से 3.01 × 10²⁰ अणु निष्कासित किए जाते हैं, तो शेष H₂SO₄ में ऑक्सीजन का द्रव्यमान ज्ञात कीजिए।

• A. 2 mg
• B. 32 mg
• C. 64 mg
• D. 16 mg

Answer 1

Answer: (B)

• One mole of sulphuric acid contains 4 moles of oxygen.

• That is 98 g of one mole of sulphuric acid contains 64 g of 4 moles of oxygen.

• The number of moles present in $3.01\times {10}^{20}$ molecules=

$=\frac{GivenNo.ofmolecules}{AvagadroNo.}$

$=\frac{3.01\times {10}^{20}}{6.022\times {10}^{23}}$

$=0.0005molesof{H}_{2}S{O}_4$

Hence the number of moles and mass of oxygen can be calculated as:

$1moleof{H}_{2}S{O}_4⟶4molesof{O}_2$

$0.0005moleof{H}_{2}S{O}_4⟶xmolesof{O}_2$

$\frac{1}{0.0005}=\frac{4}{x}$

$x=4\times 0.0005$

$=0.002molesofoxygen.$

$\therefore MassofOxygen=No.ofmoles\times massofoxygen.$

$=0.002\times 16$

$=0.032gmof{O}_2$