Question

What is the concentration of 2.9 gram NaCl in a 500 mL solution (MW of NaCl is 58)?

Select one:

a. 0.1 M

b. 0.25 M

c. 0.5 M

d. 1.0 M

e. 50 mM

Answer 1

Answer is option A i. e 0.1M

Solution:-

Formula used i.e

C = n/V

C = Molar concentration

n = number of moles

V = volume per litre

Calculate n (number of moles)

n = Mass of NaCl in gram / Molecular weight of NaCl in gram

n = 2.9 g / 58 g

As in question volume given in ml so convert firstly into L i.e 500/ 1000 L

So, C = (2.9 /58 ) × (1000 × 500 ) = 0.1 mol/L

mol/L is the Molarity ( M ) so, in place of 0.1 mol/L we place the answer is 0.1M

So the concentration of 2.9 g NaCl in 500 ml solution is 0.1 M.