Question

to reduce dangerous swelling in the brain, physicians sometimes administer intravenous hypertonic saline, a 7.0%(w/v) solution of salt (nacl) in water.
calculate the mass of nacl in 70.0 ml of this solution. be sure your answer has a unit symbol and is rounded to the correct number of significant digits.

Explanation:

Step1: Recall the formula for mass - volume percentage

The formula for mass - volume percentage \((m/v)\%\) is \((m/v)\%=\frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}}\times100\). We can rearrange it to solve for the mass of the solute: \(\text{mass of solute}=\frac{(m/v)\%\times\text{volume of solution (mL)}}{100}\)

Step2: Substitute the given values into the formula

We are given that \((m/v)\% = 7.0\%\) and the volume of the solution \(V = 70.0\space mL\).
Substitute these values into the formula: \(\text{mass of }NaCl=\frac{7.0\times70.0}{100}\space g\)

Step3: Calculate the mass

$$
LATEXBLOCK0
$$

Answer:

\(4.9\space g\)