Question

Sodium hydroxide is added to many swimming pools to neutralize excess acidity from hydrochloric acid (which is a solution of hydrogen chloride). If 0.02 moles of sodium hydroxide is added to a pool, how many grams of hydrogen chloride will be neutralized?

Answer 1

Sodium hydroxide NaOH is a strong base.
Hydrochloric acid HCl is also a strong base.

Use your knowledge of neutralization with strong bases and acids. How do the moles of H+ ions compare to the moles of OH- ions?

Answer 2

HCl is a strong acid*

Answer 3

Would the same amount of moles be neutralized?

Answer 4

Yes, neutralization means [H+] = [OH-] so you have a pH of 7.

Answer 5

Ok so how do I use that to get the correct answer?

Answer 6

Given:
0.02 mol NaOH

Find:
grams of HCl needed to neutralize.

First, write a balanced equation.

Answer 7

NaOH(0.2 M)+HCl(x M) => NaCL + H₂O ?

Answer 8

Basically correct, although you typically don't include molarity in the balanced equation.

NaOH + HCl -> NaCl + H2O

So you have the same number of Na, O, H, and Cl on both sides.

Therefore, you need a 1:1 ratio in moles to neutralize the solution. So, for every 1 mole of NaOH, you NEED 1 mole of HCl to neutralize it.

You are given 0.02 mol NaOH.
Therefore, you need 0.02 mol HCl.

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Now, find the molecular weight for 0.02 mol of HCl.

Answer 9

Molecular weight is just atomic mass right?

Answer 10

Sorry, to rephrase, find the grams of HCl when you have 0.02 mol of the solution.

Answer 11

Yes, molecular weight is the same as atomic mass in practice (but different in definition).

Answer 12

You would take the molecular weight of HCl and multiply it by 0.02 to find out the grams of HCl when you have 0.02 mol.

Use stoichiometry to help.

Answer 13

Okay, I just rounded the molecular weight to 1 for hydrogen and 35 for chlorine. And I multiplied to get 0.72

Answer 14

Same answer I got.

Answer 15

So the answer is 0.72 grams of hydrogen chloride?

Answer 16

Yes :)

Answer 17

Ok. Thank you! :D

Answer 18

No problem glad I could help.