# 27.0 L of HCl gas at STP is dissolved in water, giving 785 mL of solution. What is the molarity of the HCl solution?

9.46 M

1.53 M

0.946 M

15.3 M

None of the above is within 1% of the correct answer.

### 3 Answers

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- Roger the MoleLv 73 weeks agoBest Answer
(27.0 L) / (22.4 L/mol) / (0.785 L) = 1.5355 mol/L

So choose the second option.

- Anonymous3 weeks ago
27 L of HCl is just over 1 mole (1 mole of any ideal gas at STP occupies 22.4 L)

You can look at the choices and pick the second without pulling out the calculator.

- 3 weeks ago
27 liters at STP. At STP, 1 mole of gas occupies 22.4 Liters of space.

27/22.4 = # of moles of HCl gas. You dissolve this in 785 mL, so how many moles would you need for 1 liter?

k / (27/22.4) = 1000 / 785

k = (1000/785) * (27/22.4)

k = 27000 / (22.4 * 785)

k = 1.5354868061874431301182893539581...

1.53 M would work

thank you

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thank you very much for your help