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Some Basic Concepts of Chemistry question

2007 · Shift 0 · Q38
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Some Basic Concepts of Chemistry question

2007 · Shift 0 · Q38

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
In the reaction 2AlAlAl(s) + 6HClHClHCl(aq) →\to→ 2Al3+Al^{3+}Al3+ (aq) + 6Cl−Cl^-Cl−(aq) + 3H2H_2H2​(g)
  1. A
    11.2 L H2H_2H2​(g) at STP is produced for every mole HClHClHCl(aq) consumed
  2. B
    6 L HClHClHCl(aq) is consumed for every 3L H2H_2H2​(g) produced
  3. C
    33.6 L H2H_2H2​(g) is produced regardless of temperature and pressure for every mole that reacts
  4. D
    67.2 H2H_2H2​(g) at STP is produced for every mole Al that reacts
View written solutionFree

Correct answer: A

  1. Write the balanced reaction

2Al(s)+6HCl(aq)→2Al3+(aq)+6Cl−(aq)+3H2(g)2Al(s) + 6HCl(aq) \rightarrow 2Al^{3+}(aq) + 6Cl^-(aq) + 3H_2(g)2Al(s)+6HCl(aq)→2Al3+(aq)+6Cl−(aq)+3H2​(g)

From the balanced equation:

  • 666 mol HClHClHCl produce 333 mol H2H_2H2​
  • 222 mol AlAlAl produce 333 mol H2H_2H2​

  1. Find the mole ratio between HClHClHCl and H2H_2H2​

6 mol HCl→3 mol H26\text{ mol }HCl \rightarrow 3\text{ mol }H_26 mol HCl→3 mol H2​

Dividing by 333:

2 mol HCl→1 mol H22\text{ mol }HCl \rightarrow 1\text{ mol }H_22 mol HCl→1 mol H2​

So for every 111 mol HClHClHCl consumed:

1 mol HCl→12 mol H21\text{ mol }HCl \rightarrow \frac{1}{2}\text{ mol }H_21 mol HCl→21​ mol H2​

At STP, 111 mol gas occupies 22.4 L22.4\,L22.4L.

Therefore, 12\frac{1}{2}21​ mol H2H_2H2​ occupies:

12×22.4=11.2 L\frac{1}{2}\times 22.4 = 11.2\,L21​×22.4=11.2L

So Option A is correct.


  1. Check each option

Option A

"11.2 L11.2\,L11.2L H2H_2H2​ at STP is produced for every mole HClHClHCl consumed"

As shown above:

1 mol HCl→12 mol H2=11.2 L at STP1\text{ mol }HCl \rightarrow \frac{1}{2}\text{ mol }H_2 = 11.2\,L \text{ at STP}1 mol HCl→21​ mol H2​=11.2L at STP

✅ Correct


Option B

"6 L6\,L6L HCl(aq)HCl(aq)HCl(aq) is consumed for every 3 L3\,L3L H2(g)H_2(g)H2​(g) produced"

This compares volume of aqueous HCl solution with volume of gas. For solutions, volume depends on concentration, so liters of HCl(aq)HCl(aq)HCl(aq) cannot be directly obtained from stoichiometric coefficients unless concentration is specified.

Hence this statement is not generally valid.

❌ Incorrect


Option C

"33.6 L33.6\,L33.6L H2H_2H2​ is produced regardless of temperature and pressure for every mole that reacts"

33.6 L33.6\,L33.6L corresponds to:

33.622.4=1.5 mol H2\frac{33.6}{22.4} = 1.5\text{ mol }H_222.433.6​=1.5 mol H2​

This is the amount produced when:

1 mol Al→32 mol H21\text{ mol }Al \rightarrow \frac{3}{2}\text{ mol }H_21 mol Al→23​ mol H2​

But gas volume is not independent of temperature and pressure. 33.6 L33.6\,L33.6L is only true at STP, not regardless of TTT and PPP.

❌ Incorrect


Option D

"67.267.267.2 H2(g)H_2(g)H2​(g) at STP is produced for every mole AlAlAl that reacts"

From stoichiometry:

2 mol Al→3 mol H22\text{ mol }Al \rightarrow 3\text{ mol }H_22 mol Al→3 mol H2​

So,

1 mol Al→32 mol H21\text{ mol }Al \rightarrow \frac{3}{2}\text{ mol }H_21 mol Al→23​ mol H2​

At STP:

32×22.4=33.6 L\frac{3}{2}\times 22.4 = 33.6\,L23​×22.4=33.6L

Not 67.2 L67.2\,L67.2L.

❌ Incorrect


  1. Final conclusion

The only correct option is:

A\boxed{A}A​

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