Question

41. Calculate the mass of Na
ml of a semimolar solution.
(2) 3.58 g
(1) 1.35g
(4)2.92 g
(3) 4.20 g
​

Answer 1

Answer:

Your starting point here will be the definition of molarity.

As you know, molarity is defined as the number of moles of solute present in exactly

1 L

of solution. This implies that a

1-M

solution will contain

1

mole of solute in

1 L

of solution.

In your case, a

2.5-M

solution will contain

2.5

moles of sodium chloride, your solute, for every

1 L

of solution. It follows that this sample must contain

0.5

L solution

⋅

required molarity



2.5 moles NaCl

1

L solution

=

1.25 moles NaCl

Now, to convert this to grams of sodium chloride, you must use the mass of

1

mole of this compound as a conversion factor. The mass of

1

mole of sodium chloride is given by its molar mass