Question

Noke Lew weighs out 50.0 g of sodium chloride (NaCl) salt. She
adds 300.0 g of water, so her total solution mass equals the salt
plus the water together. Calculate the **percent by
mass** of NaCl in her solution. Answer to 3 significant
figures with appropriate units.

Doc Inmaking creates another solution by weighing 18.34 mg
(0.01834 g) of Vitamin C with an analytical balance. He dissolves
it in water to a total volume of 250.0 mL using a volumetric flask.
He knows he has a dilute aqueous solution, so when he calculates
the parts per million of Vitamin C he can use the shortcut.
Calculate the **parts per million** of Vitamin C in
Doc’s solution. Answer to 4 significant figures with appropriate
units.

Answer #1

**Mass of NaCl = 50 gm**

**Mass of solution = Mass of water + Mass of NaCl
added**

**=> 300 + 50**

**=> 350 gm of solution**

**Percent by mass of NaCl = (Mass of NaCl/Mass of
solution) * 100**

**=> 50/350 * 100**

**=> 100/7 = 14.2857**

**Answer in three significant figures = 14.3%**

**2)**

**ppm = 1 mg solute per Liter of solution**

**Amount of Solute = 18.34 mg**

**Volume of solution = 250 mL = 0.25 L**

**Hence ppm of Vitamin C = 18.34/0.25 ppm = 73.36
ppm**

**Hence the answer to four significant figures is 73.36
ppm or mg/L**

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