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Topic: Two questions about basic chemistry  (Read 1966 times)

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Offline nmego

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Two questions about basic chemistry
« on: February 11, 2018, 08:11:01 AM »




For the first question, I think it obvious that hydrogen gas evolves, but I'm not sure whether it is endothermic or exothermic, of course, Aluminum is more active than Hydrogen.

As for the second question, I think it was solved by the law:

Concentration1 / number1  = Concentration2 / number2

So,

0.1 / 22 = x / 10 and just solve for x, but I'm not sure

Offline chenbeier

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Re: Two questions about basic chemistry
« Reply #1 on: February 11, 2018, 08:35:41 AM »
For the first one you have to consider, get it hot or not? Then decide.

The second one  you have to calculate how much mole H+ you have. What is the formula of sulfuric acid? These H+ has to be neutralized.

Offline nmego

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Re: Two questions about basic chemistry
« Reply #2 on: February 11, 2018, 08:49:47 AM »
For the first one you have to consider, get it hot or not? Then decide.

The second one  you have to calculate how much mole H+ you have. What is the formula of sulfuric acid? These H+ has to be neutralized.

I think it wouldn't be hot, therefore it would be endothermic?

It would be H2SO4 + 2NaOH = Na2SO4 + 2H2O

We see that the number of moles for NaOH is about 2 for each 1 mole of H2SO4


Offline chenbeier

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Re: Two questions about basic chemistry
« Reply #3 on: February 11, 2018, 08:56:17 AM »
For the first one you had 50% chance to get the right answer, but you choose the wrong one.It gets really hot . The heat helpes to clean the pipework. So its exotherm.


Second one is correct, now you can calculate the concentration.

Offline Borek

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Re: Two questions about basic chemistry
« Reply #4 on: February 11, 2018, 09:02:38 AM »
As for the second question, I think it was solved by the law:

Concentration1 / number1  = Concentration2 / number2

There is no such law, whoever taught you that, was wrong.

However, this is a simple stoichiometry, start with the reaction equation and follow from that.
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