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Some Basic Concepts of Chemistry question

2022 · 24 Jun · Shift 1 · Q1
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Some Basic Concepts of Chemistry question

2022 · 24 Jun · Shift 1 · Q1

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
If a rocket runs on a fuel (C15H30C_{15}H_{30}C15​H30​) and liquid oxygen, the weight of oxygen required and CO2CO_2CO2​ released for every litre of fuel respectively are : (Given : density of the fuel is 0.756 g/mL)
  1. A
    1188 g and 1296 g
  2. B
    2376 g and 2592 g
  3. C
    2592 g and 2376 g
  4. D
    3429 g and 3142 g
View written solutionFree

Correct answer: C

  1. Write the combustion reaction

For the fuel C15H30C_{15}H_{30}C15​H30​:

C15H30+O2→CO2+H2OC_{15}H_{30} + O_2 \rightarrow CO_2 + H_2OC15​H30​+O2​→CO2​+H2​O

Balancing carbon and hydrogen first:

C15H30+O2→15CO2+15H2OC_{15}H_{30} + O_2 \rightarrow 15CO_2 + 15H_2OC15​H30​+O2​→15CO2​+15H2​O

Now balance oxygen on the right:

  • In 15CO215CO_215CO2​, oxygen atoms =15×2=30= 15 \times 2 = 30=15×2=30
  • In 15H2O15H_2O15H2​O, oxygen atoms =15×1=15= 15 \times 1 = 15=15×1=15

Total oxygen atoms required =45= 45=45, so:

C15H30+452O2→15CO2+15H2OC_{15}H_{30} + \frac{45}{2}O_2 \rightarrow 15CO_2 + 15H_2OC15​H30​+245​O2​→15CO2​+15H2​O

Thus, for 111 mole of fuel:

  • 452\dfrac{45}{2}245​ moles of O2O_2O2​ are required
  • 151515 moles of CO2CO_2CO2​ are produced

  1. Mass of 1 litre of fuel

Given density of fuel:

0.756 g mL−10.756\ \text{g mL}^{-1}0.756 g mL−1

Since:

1 L=1000 mL1\ \text{L} = 1000\ \text{mL}1 L=1000 mL

Mass of 111 litre fuel:

m=0.756×1000=756 gm = 0.756 \times 1000 = 756\ \text{g}m=0.756×1000=756 g


  1. Moles of fuel in 1 litre

Molar mass of C15H30C_{15}H_{30}C15​H30​:

15(12)+30(1)=180+30=210 g mol−115(12) + 30(1) = 180 + 30 = 210\ \text{g mol}^{-1}15(12)+30(1)=180+30=210 g mol−1

So moles of fuel:

n=756210=3.6 moln = \frac{756}{210} = 3.6\ \text{mol}n=210756​=3.6 mol


  1. Oxygen required

From the balanced equation, 111 mole fuel requires 452=22.5\dfrac{45}{2} = 22.5245​=22.5 moles O2O_2O2​.

So for 3.63.63.6 moles fuel:

n(O2)=3.6×22.5=81 moln(O_2) = 3.6 \times 22.5 = 81\ \text{mol}n(O2​)=3.6×22.5=81 mol

Mass of oxygen required:

m(O2)=81×32=2592 gm(O_2) = 81 \times 32 = 2592\ \text{g}m(O2​)=81×32=2592 g


  1. Carbon dioxide released

From the balanced equation, 111 mole fuel gives 151515 moles CO2CO_2CO2​.

So for 3.63.63.6 moles fuel:

n(CO2)=3.6×15=54 moln(CO_2) = 3.6 \times 15 = 54\ \text{mol}n(CO2​)=3.6×15=54 mol

Mass of carbon dioxide released:

m(CO2)=54×44=2376 gm(CO_2) = 54 \times 44 = 2376\ \text{g}m(CO2​)=54×44=2376 g


  1. Match with options

Required values are:

  • Oxygen required =2592 g= 2592\ \text{g}=2592 g
  • CO2CO_2CO2​ released =2376 g= 2376\ \text{g}=2376 g

This matches Option C.


  1. Comparison with stored correct answer

Stored correct answer: C

My derived answer: C

So, they agree.

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