Question

A student takes a measured volume of 3.00 M HCl to prepare a 50.0 mL sample of 1.80 M HCL. What volume of 3.00 M HCI

did the student use to make the sample?
Use MV - MV
Sos
3.70 ml
16.7 ml
300 ml
83.3 ml
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Answer 1

30.0 ml

Step-by-step explanation:

1.8 M means 1.8 moles of HCl in 1 liter (or 1000 ml) of solution.

50 ml of solution has:

1.8 moles/(x moles) = 1000 ml/(50 ml)

x = 1.8 moles/(1000 ml) * 50 ml = 0.09 moles

3 M means 3 moles of HCl in 1 liter of solution.

0.09 moles are found in:

3 moles/(0.09 moles) = 1000 ml/(x ml)

x = 0.09 moles * 1000 ml/(3 moles) = 30 ml

Then, you have to take a sample of 30 ml of a solution 3 M and add 20 ml of the solvent (probably water) to make 50 ml of solution 1.8 M of HCl.

Answer 2

To solve the question you use the following formula:

concentration (1) × volume (1) = concentration (1) × volume (1)

3 M × volume (1) = 1.8 M × 50 mL

volume (1) = (1.8 M × 50 mL) / 3 M = 30 mL