Question

How many grams of NaCl are needed to make 25 ml of a 4 mg/ml solution?

Answer 1

Answer

Therefore, the mass in grams of NaCl in the solution = 0.1 grams

Explanation

Given:

Volume = 25 mL

Concentration of the solution in mg/mL = 4 mg/mL

What to find:

The mass in grams of NaCl in the solution.

Solution:

Concentration, C in mg/mL = Mass, (m) / Volume (V) i.e

$C=\frac{m}{V}$

Putting C = 4mg/mL, and V = 25 mL into the formula, we have

$\begin{gathered} 4\text{ }mg\text{/}mL=\frac{m}{25\text{ }mL} \\ \\ \Rightarrow m=4\text{ }mg\text{/}mL\times25\text{ }mL \\ \\ m=100\text{ }mg \end{gathered}$

The final step is to convert 100 mg to grams.

Conversion factor:

1 mg = 10⁻³ grams

So 100 mg ⇒ (100mg/1 mg) x 10⁻³ grams = 0.1 grams.

Therefore, the mass in grams of NaCl to make the solution = 0.1 grams.