Question #216ab

1 Answer
Apr 14, 2017

"0.083 L"0.083 L of concentrated 12.0M12.0M HNO_3HNO3

Explanation:

This is a dilution chemistry problem. For problems like this one, use the following equation

color(white)(aaaaaaaaaaaaaaaa)aaaaaaaaaaaaaaaaM_1V_1 = M_2V_2M1V1=M2V2

Where
M_1 = "molarity of solution 1"M1=molarity of solution 1
V_1 = "volume of solution 1"V1=volume of solution 1
M_2 = "molarity of solution 2"M2=molarity of solution 2
V_2 = "volume of solution 2"V2=volume of solution 2

Whenever you dilute a concentrated stock solution, or for that matter, any solution, you are essentially changing the volume of that solution by adding water. If we look at what "Molarity"Molarity exactly is,

"Molarity" = "moles"/(1" Liter solution")Molarity=moles1 Liter solution

you can see when you increase the "volume"volume, you decrease the "molarity"molarity (concentration). In dilution cases, you are adding water so moles of the solute do not change, only the volume of the solution changes.

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Using our equation from above, we can find the number of moles of nitric acid, HNO_3HNO3, from what we are given.

We will let M_1M1 and V_1V1 be 8.0 M8.0M and 125" mL"125 mL respectively. Make sure to convert "mL"mL to "L"L first. For M_2M2, use the 12.0M12.0M. Isolate V_2V2 and solve.

  • M_1V_1 = M_2V_2M1V1=M2V2

  • (0.125L)(8.0M) = (12.0M)(V_2)(0.125L)(8.0M)=(12.0M)(V2)

  • ((0.125L)(8.0cancelM))/(12.0cancelM) = V_2

  • "0.083 L"= V_2

Answer: 0.083 L