Textbook Problem

1 views

The structure of one of the bases in DNA, adenine, is shown here. Which represents the greater mass: 40.0 g of adenine or 3.0 × 10²³ molecules of the compound?

Interpretation Introduction

Interpretation: It should be determined that which represents the greater mass, $40.0g$ of adenine or $3.0\times {10}^{23}$ molecules of the compound.

Concept introduction:

• $\text{Amount}\text{of}\text{substance}\text{(mole)}=\frac{\text{Given}\text{mass}\text{of}\text{the}\text{substance}}{\text{Molar}\text{mass}}$
• $\text{Number}\text{of}\text{moles}=\frac{\text{Number}\text{of}\text{molecule}}{\text{Avogadro}\text{Number}}$
• $\text{Mass}\text{of}\text{the}\text{substance}\text{=}\text{Amount}\text{of}\text{the}\text{substance}\text{×}\text{Molar}\text{mass}$
• The molar mass of an element or compound is the mass in grams of 1 mole of that substance, and it is expressed in the unit of grams per mol (g/mol

Explanation of Solution

Adenine one of the nitrogen base in DNA.

Molecular formula of adenine is $C_5{H}_5{N}_5$ therefore its molecular formula is $135.13g/mol$ since $\begin{array}{l}C\Rightarrow 5\times 12.0107\\ H\Rightarrow 5\times 1.00794\\ N\Rightarrow 5\times 14.0067\\ Totally=135.13\text{g/mol}\end{array}$

The mass of $3.0\times {10}^{23}$ molecules of the compound can be calculated as follows,

$\begin{array}{l}\text{Mass of 3}\text{.0}{\text{×10}}^{\text{23}}\text{molecules of adenine}\text{=}\frac{\text{3}}{}\end{array}$