Question

A solid sample (Sample 1) is analyzed and found to contain 1.47 g carbon and 0.123 g hydrogen. A second sample (Sample 2) is expected to be composed of the same pure compound. If Sample 2 is found to contain 2.17 g hydrogen, how much carbon is expected in the sample ?

Answer 1

Explanation:

Here it is given that carbon is sample 2 = 25.9 g

• For sample 1,  mass carbon = 1.47 g

No. of moles of carbon will be calculated as follows.

         No. of moles of carbon = $\frac{\text{mass carbon}}{\text{molar mass carbon}}$

                                                 = $\frac{1.47 g}{12.01 g/mol}$

                                                 = 0.1224 mol

It is also given that mass of hydrogen = 0.123 g

Hence, calculate number of moles of hydrogen as follows.

           No. of moles of hydrogen = $\frac{\text{mass hydrogen}}{\text{molar mass hydrogen}}$

                                                      = $\frac{0.123 g}{1.008 g/mol}$

                                                      = 0.122 mol

Therefore, $\frac{\text{moles of carbon}}{\text{moles of hydrogen}}$

                              = $\frac{0.1224 mol}{0.122 mol}$

                                = 1.003

• For sample 2,  mass of hydrogen = 2.17 g

Therefore, calculate the number of moles of hydrogen as follows.

       No. of moles of hydrogen = $\frac{\text{mass hydrogen}}{\text{molar mass hydrogen}}$

                                          = $\frac{2.17 g}{1.008 g/mol}$

                                          = 2.1528 mol

Hence, calculate the moles of carbon as follows.

      Moles of carbon = $\text{moles hydrogen} \times \frac{\text{moles of carbon}}{\text{moles hydrogen}}$

                                   = $2.1528 mol \times 1.003$

                                  = 2.16 mol

Mass of carbon = moles carbon × molar mass carbon

                           = (2.16 mol) × (12.01 g/mol)

                           = 25.9 g

Thus, we can conclude that 25.9 g of carbon is expected in the sample.