Question

7. Sometimes, especially in the clinical lab, concentrations will be expressed in percentage rather than molarity. The percentage concentration refers to the number of grams of solute dissolved in 100 ml of solution (eg. a 5 % solution of sucrose contains 5 g of sucrose in 100 ml of water). Normal saline, a solution that is isotonic with human blood, is a 0.85 percent solution of sodium chloride. What is the molar concentration of normal saline

Answer 1

Answer:

The molar concentration of normal saline is 0.15 mol/L.

Explanation:

The mass of NaCl in 0.85% of normal saline is:

$0.85 \% = \frac{0.85 g}{100 ml}$

$m_{NaCl} = 0.85 g$

The molar concentration can be found using the following equation:

$C = \frac{n}{V}$        

So we need to find the number of moles of NaCl in 1 liter of solution.

$m_{NaCl} = \frac{0.85 g}{100 mL}*\frac{1000 mL}{1 L}*1 L = 8.5 g$

$n = \frac{m_{NaCl}}{M}$

Where:

M: is the molar mass of NaCl = 58.44 g/mol

$n = \frac{8.5 g}{58.44 g/mol} = 0.15 moles$

Hence, the molar concentration is:

$C = \frac{0.15 moles}{1 L} = 0.15 mol/L$        

Therefore, the molar concentration of normal saline is 0.15 mole per liter.

                                 

I hope it helps you!