Chemistry questions

Question

What is the mass of sodium chloride used to create a 250 mL solution at a concentration of 3.5 M? To earn credit, your solution must include a step-by-step solution with units included throughout to support your final answer.

Answer 1

The definition of 3.5 M NaCl is 3.5 moles of NaCl per liter of solution.

Molar mass NaCl = 58.4 g / mole

Step 1: find grams NaCl needed for 1 liter. 3.5 moles NaCl = 3.5 moles x 1 58.4 g / mol = 204.4 g/L

Step 2: convert 250 mls of solution to liters. 250 mls x 1 / 1000 mls = 0.250 L

Step 3: find grams NaCl needed for 0.250 L. 0.250 L x 204.4 g/L = 51 g NaCl / 0.250 L (to 2 sig.figs.)

Another way:

3.5 mol / L x 0.250 L x 58.4 g / mol = 51 g NaCl