20 grams NaCl are dissolved in water to make a 0.85 M solution. What is the volume of the solution in mL

Question

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Answer 1

0.85 M = 0.85 moles NaCl / liter

20 g NaCl x 1 mol NaCl / 58.4 g = 0.342 moles

So, we now know the moles we have and we need to find the volume (in liters) to make it 0.85 mol / L

0.342 mols / x L = 0.85 mol / 1 L

x = 0.403 L = 403 mls = 400 mls (1 sig. fig.)*

Or you could solve as follows:

(0.85 mol / L) (x L) = 0.342 mols

x = 0.342 / 0.85 = 0.402 L = 402 mls = 400 mls (1 sig. fig.)*

*one significant figure based on the value of 20 g NaCl which has only 1 s.f.

Answer 2

no. of moles of NaCl = 20g/58.44g/mole

= 0.342 mole NaCl

volume of NaCl = no. of mole NaCl/concentration of NaCl

= 0.342 mole NaCl/0.85M

= 0.403 mL