Chapter U4.77, Problem 4E

Interpretation Introduction

Interpretation:

Between the given molecules, the molecule having more number of moles should be determined.

1.0 g methanol and 1.0 g ethanol

Concept Introduction:

Mole is SI unit which is used to measure the quantity of the substance. It is the quantity of a substance which contains same number of atoms as present in accurately 12.00 g of carbon-12 is known as mole

Number of moles is defined as the ratio of mass to the molar mass.

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

The ratio of mass of the given compound to the number of moles of compound is known as molar mass.

The one mole of any substance is equal to the Avogadro number i.e. $6.022\times {10}^{23}$ atoms.

Answer to Problem 4E

Number of moles of 1.0 g of methanol is greater than the number of moles of 1.0 of ethanol.

Explanation of Solution

The given two molecules are: 1.0 g methanol ( ${\text{CH}}_{\text{4}}\text{O}$ ) and 1.0 g ethanol ( ${\text{C}}_{\text{2}}{\text{H}}_{\text{6}}\text{O}$ ).

First step is to calculate the molar mass of each molecule.

Molar mass of methanol = $\text{1}\times \text{12}\text{.0107 g/mole + 4}\times \text{1}\text{.00784 g/mole + 1}\times \text{15}\text{.99 g/mole}$

= $32.032\text{ g/mole}$

Molar mass of ethanol = $\text{2}\times \text{12}\text{.0107 g/mole + 6}\times \text{1}\text{.00784 g/mole + 1}\times \text{15}\text{.99 g/mole}$

= $46.06\text{ g/mole}$

Now,

Number of moles of methanol is calculated as:

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

Put the values,

Number of moles of methanol = $\frac{\text{1}\text{.0 g}}{\text{32}\text{.032 g/mole}}$

Number of moles of methanol = $\text{0}\text{.031218 mole}$

Number of moles of ethanol is calculated as:

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

Number of moles of ethanol = $\frac{\text{1}\text{.0 g}}{46.06\text{ g/mole}}$

Number of moles of ethanol = $\text{0}\text{.02171 mole}$

Therefore, number of moles of 1.0 g of methanol is greater than number of moles of 1.0 of ethanol.