Question

How do I prepare a solution of sodium nitrite with a concentration of 38.5 mmol/L?

Answer 1

You dissolve 2.66 g of sodium nitrite in enough water to make 1 L of solution.

Explanation:

You must measure out 38.5 mmol of sodium nitrite.

Step 1. Calculate the molar mass of

NaNO

2

M

r

=

Na + N + 2O

=

(22.99 + 14.01 + 2×16.00)

=

69.00

∴ The mass of 1 mol of

NaNO

2

is 69.00 g.

Step 2. Calculate the mass of 38.5 mmol of

NaNO

2

Mass of NaNO

2

=

38.5

×

10

-3

mol NaNO

2

×

69.00 g NaNO

2

1

mol NaNO

2

=

2.66 g NaNO

2

Step 3. Prepare the solution

Transfer the

NaNO

2

to a 1 L volumetric flask.

Add about 300 mL of distilled water and swirl to dissolve the sodium nitrite.

Then add water until the bottom of the meniscus is just at the mark on the volumetric flask.