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Question: Which of the following contain the maximum number of molecules? A. \(1g{\text{ }}C{O_2}\) B. \(1...

Which of the following contain the maximum number of molecules?
A. 1g CO21g{\text{ }}C{O_2}
B. 1g N21g{\text{ }}{N_2}
C. 1g H21g{\text{ }}{H_2}
D. 1g CH41g{\text{ }}C{H_4}

Explanation

Solution

We can solve the above problem with the help of mole concept. According to it, the mass of one mole of atoms is equal to the gram atomic mass. The formula used is:
Number of molecules in “w” gram of an element =w×6.023×1023gram molecular mass\dfrac{{w \times 6.023 \times {{10}^{23}}}}{{gram{\text{ }}molecular{\text{ }}mass}}

Complete step by step answer: In case of 1g1g of CO2C{O_2}, let us calculate the gram molecular mass of CO2.C{O_2}. As we know the gram atomic mass of CC is 12g12g and the gram atomic mass of OO is 16g.16g. Then the gram atomic mass of CO2C{O_2} is calculated as given below:
12+2×16 12+32=44g  12 + 2 \times 16 \\\ \Rightarrow 12 + 32 = 44g \\\
Number of molecules in 1g1g of CO2C{O_2} is calculated as below:
1×6.023×102344\dfrac{{1 \times 6.023 \times {{10}^{23}}}}{{44}}
6.023×102344=0.1368×1023\Rightarrow \dfrac{{6.023 \times {{10}^{23}}}}{{44}} = 0.1368 \times {10^{23}}
Now in the case of 1g1 g of N2N_2, as we know the gram atomic mass of N2N_2 is 28g.28g. Then the number of molecule is calculate as below:
1×6.023×102328=0.21×1023\dfrac{{1 \times 6.023 \times {{10}^{23}}}}{{28}} = 0.21 \times {10^{23}}
For the case of 1g of H2H_2 ,the gram atomic mass of H2H_2 is 2g.2g. The the number of molecules is calculated as below:
1×6.023×10232=3.011×1023\dfrac{{1 \times 6.023 \times {{10}^{23}}}}{2} = 3.011 \times {10^{23}}
For 1g CH4.C{H_4}.The gram atomic mass of methane is
12+4=16g12 + 4 = 16g
Number of molecules are:
1×6.023×102316=0.376\dfrac{{1 \times 6.023 \times {{10}^{23}}}}{{16}} = 0.376
Hence the correct answer is option C.

Note: The number of molecules can be alternatively calculated as:
If we take the case of CO2,C{O_2}, 44g44g of the CO2C{O_2} contains molecules=6.023×10236.023 \times {10^{23}}. So, the number of molecules in 1g1 g of carbon dioxide is calculated as below:
6.023×102344=0.136×1023\dfrac{{6.023 \times {{10}^{23}}}}{{44}} = 0.136 \times {10^{23}}
Now, if we consider the case of N2,N_2, 28g28g of nitrogen contains molecules =6.023×10236.023 \times {10^{23}}. So 1g1 g of nitrogen contains
6.023×102328=0.215 molecules\dfrac{{6.023 \times {{10}^{23}}}}{{28}} = 0.215{\text{ molecules}}
For the case of H2H_2, 2g of hydrogen contains molecules= 6.023×10236.023 \times {10^{23}}. So 1 g of hydrogen contains
6.023×10232=3.0115 molecules\dfrac{{6.023 \times {{10}^{23}}}}{2} = 3.0115{\text{ molecules}}
For the case of CH4CH_4, 16g of the methane contain molecules=6.023×10236.023 \times {10^{23}}. So 1g1 g of methane contains
6.023×102316=0.376 molecules\dfrac{{6.023 \times {{10}^{23}}}}{{16}} = 0.376{\text{ molecules}}