Berkeley Review Acid/Base Questions 4.12 & 4.13

[salsasunrise123]

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Hi, I am really stuck on example 4.13 and cannot reconcile the approach to answering it with example 4.12. I was hoping someone could walk me through 4.13. I don't understand why you are multiplying CaCO3 by 2. I would think you would multiply HCl by 2. Can someone please explain it to me in simple terms. Explain it to me like I'm a 6th grader bc I am lost. I also don't get how the approach you take for 4.13 is different from 4.12. Thanks so much! I have reproduced each question below:

4.12 How many ml of .4 M NaOH are required to neutralize 100 ml .25 M H2SO4?
answer: 125

4.13 How many ml of .6 HCl are required to neutralize 3 grams of Caco3?
Answer 100 ml

 

[TheUPSIDEdown]

So, for the second question, 4.13:

Start with the balanced equation. Whenever you see the world neutralize you should immediately think of an equation. You should also know that when you mix Acid + Base --> Salt + water

Therefore, your balanced equation is this:
2HCl + CaCO3 --> CaCl2 (salt) + H2O (water) + CO2 (whatever is left)

Now start with what you're given.

3 gram CaCO3/1 X 1 mol CaCO3/100gCaCO3 X 2 mol HCl/1 mol CaCO3 X 1000mL HCl/0.6 mol HCl = 100mL HCl

I bolded where you've been confused. That is the step where you multiply by two. Apply the same reasoning to the other question.

Hope this helps.