Chapter 14, Problem 126SAE

Interpretation Introduction

(a)

Interpretation:

The concentration of Na+ in blood should be calculated.

Concept introduction:

The density can be calculated from mass and volume as follows:

$\begin{array}{l}d=\frac{m}{v}\\ m=dv\end{array}$

From mass and molar mass, number of moles can be calculated as follows:

$n=\frac{m}{{\text{M}}_{\text{w}}}$

Also,

$n=cv$

Here, n is number of moles, c is concentration and v is volume.

Thus,

$c=\frac{n}{v}=\frac{m}{{\text{M}}_{\text{w}}v}$

Interpretation Introduction

(b)

Interpretation:

The concentration of ions in blood should be calculated.

Concept introduction:

The $\mathrm{NaCl}$ is salt formed from sodium and chloride ion thus,

${\text{Na}}^{\text{+}}{\text{: Cl}}^{\text{-}}\text{=1:1}$

Also,

$\begin{array}{l}[{\text{Na}}^{\text{+}}]=\left[{\text{Cl}}^{\text{-}}\right]=\left[\text{NaCl}\right]\\ [\text{ions}]=[{\text{Na}}^{\text{+}}]+\left[{\text{Cl}}^{\text{-}}\right]\end{array}$

Interpretation Introduction

(c)

Interpretation:

The osmotic pressure at 37 °C, should be calculated.

Concept introduction:

The number of moles is related to concentration and volume as follows:

$\begin{array}{l}n=cv\\ c=\frac{n}{v}\end{array}$

The osmotic pressure is calculated as follows:

$\begin{array}{l}\pi v=n\text{R}T\\ \pi =\frac{n}{v}\text{R}T\end{array}$

Or,

$\pi =c\text{R}T$

Interpretation Introduction

(d)

Interpretation:

The approximate freezing point of blood should be calculated.

Concept introduction:

The depression in freezing point can be calculated as follows:

$\Delta T_f=-{\text{K}}_{\text{f}}·m$

Here,

$\begin{array}{l}\Delta T_f\text{is the freezing-point depression }\\ {\text{K}}_{\text{f}}\text{is}\text{proportionality constants}\\ m\text{is}\text{solute molality}\end{array}$