Question

Question 14
2 pts
A chemist wants to make 100 mL of a 0.500 M solution of NaCl. They have a
stock solution of 1.2 M NaCl. How much of the original stock solution do they
need to make their new dilute solution?

Answer 1

They will need 42 mL of the stock solution

Explanation:

From the question given above, the following data were obtained:

Molarity of stock solution (M₁) = 1.2 M

Molarity of diluted solution (M₂) = 0.5 M

Volume of diluted solution (V₂) = 100 mL

Volume of stock solution needed (V₁) =?

The volume of stock solution needed can be obtained by using the dilution formula as illustrated below:

M₁V₁ = M₂V₂

1.2 × V₁ = 0.5 × 100

1.2 × V₁ = 50

Divide both side by 1.2

V₁ = 50 / 1.2

V₁ ≈ 42 mL

Thus, 42 mL of the stock solution is needed.

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Answer 2

Answer:

They need 41.7 mL of the original stock solution.

Explanation:

We can use the following equation for dilutions:

Cc x Vc = Cd x Vd

Where Cc and Vc are the concentration and volume values in the concentrated condition, whereas Cd and Vd are the concentration and volume values in the diluted condition.

The concentrated solution is the original stock solution, and it has:

Cc = 1.2 M

The diluted solution must be:

Cd = 0.500 M

Vd = 100 mL

So, we have to calculate Vc. For this, we replace the data in the equation:

$V_{c} = \frac{C_{d} V_{d} }{C_{c} } = \frac{(0.500 M)(100 mL)}{1.2 M} = 41.7 mL$

Therefore, 41.7 mL of 1.2 M original stock solution are required to make 100  mL of a diluted solution with a concentration of 0.500 M.