Question

what is the new concentration of A if 7.7 ml of a .10 M solution of A is mixed with 18.3 mL of .20 M solution B and an additional 11.7 ml water?

Answer 1

0.12 M

Step-by-step explanation:

To find the new concentration, you need to (1) find the moles of Solution A (via the molarity equation), then (2) find the moles of Solution B, then (3) combine all of the moles and volumes, and then (4) calculate the new molarity. The final answer should have 2 sig figs to reflect the lowest amount of sig figs in the given values.

Solution A:

7.7 mL / 1,000 = 0.0077 L

Molarity = moles / volume

0.10 M = moles / 0.0077 L

0.00077 = moles

Solution B:

18.3 mL / 1,000 = 0.0183 L

Molarity = moles / volume

0.20 M = moles / 0.0183 L

0.00366 = moles

New Solution:

11.7 mL / 1,000 = 0.0117 L

New Volume = 0.0077 L + 0.0183 L + 0.0117 L

New Volume = 0.0377 L

New Moles = 0.00077 moles + 0.00366 moles

New Moles = 0.00443 moles

Molarity = moles / volume

Molarity = 0.0043 moles / 0.0377 L

Molarity = 0.1175 M = 0.12 M