Chapter 2, Problem 2.27P

Interpretation Introduction

Interpretation:

The required mass of ${\text{KNO}}_{\text{3}}$ to prepare $\text{500}\text{mL of }\text{1}\text{.000 M}$ at $\text{20°C}$ solution should be determined.

Concept introduction:

Correction for thermal expansion:

The temperature changes are make a changes in concentration (molarity) of the solutions and this concentration change at given temperature is calculated by mathematical method is known as correction for thermal expansion.

$\frac{\text{c'}}{\text{d'}}\text{ =}\frac{\text{c}}{\text{d}}$

Where,

$\text{c'}$ is concentration of solution at temperature.

$\text{d'}$ is density of solution at temperature.

$\text{c}$ is concentration of solution at apply temperature.

$\text{d}$ is the density of solution at apply temperature.

Interpretation Introduction

Interpretation:

The apparent mass of ${\text{KNO}}_{\text{3}}$ at $\text{20}°\text{C}$ has to be calculated.

Concept introduction:

Buoyancy Correction:

The weight of the object in air is less then weight of the object in vacuum because of buoyancy, this weight variation is corrected using Buoyancy equation it is,

$\text{m}\text{=}\frac{\text{m'}\left(\text{1-}\frac{{\text{d}}_{\text{a}}}{{\text{d}}_{\text{w}}}\right)}{\left(\text{1-}\frac{{\text{d}}_{\text{a}}}{\text{d}}\right)}$

Where,

$\text{m}$ is mass of object in vacuum.

$\text{m'}$ is mass of object in air (read on a balance).

${\text{d}}_{\text{a}}$ is the density of air $\left(\text{0}\text{.001 2 g/mL near I bar and 25°C}\right)$.

${\text{d}}_{\text{w}}$ is the density of calibration weights $\text{(8}\text{.0 g/mL)}$.

$\text{d}$ is the density of the object being weighed.