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1. 25cm3 of sodium hydroxide reacts with 21cm3 of 0.2 mol dm-3 HCl. calculate the molarity.

I really don't know how to work this out, can anyone show me the method please?
2. (Original post by Krish.)
25cm3 of sodium hydroxide reacts with 21cm3 of 0.2 mol dm-3 HCl. calculate the molarity.

I really don't know how to work this out, can anyone show me the method please?
You don't have a concentration for the sodium hydroxide so the question in this form is impossible.
3. (Original post by js374)
You don't have a concentration for the sodium hydroxide so the question in this form is impossible.
Hmm my textbook says it works. The answer's 0.168 mol dm-3 but i have no idea how to get that answer
4. (Original post by Krish.)
Hmm my textbook says it works. The answer's 0.168 mol dm-3 but i have no idea how to get that answer
write out the balanced equation

find the equivalent moles of each reacting from the equation

moles = molarity x volume (litres)

take it from there...
5. (Original post by Krish.)
Hmm my textbook says it works. The answer's 0.168 mol dm-3 but i have no idea how to get that answer
25cm3 of sodium hydroxide reacts with 21cm3 of 0.2 mol dm-3 HCl. calculate the molarity.

Ignore me, I was over-thinking the question (though it should say calculate the molarity of the sodium hydroxide)

The reaction is an acid + base = salt + water reaction.

First work out the balanced equation for NaOH and HCl ---> Salt + water

Then work out the moles of HCl present.

You can then calculate the number of NaOH in the reaction by multiplying the number of moles of HCl by the ratio NaOH to HCl which you calculated earlier.

This value is the number of moles of NaOH in 25cm3. To get to the answer you need to multiply that number so that it is in dm3.
6. (Original post by js374)
25cm3 of sodium hydroxide reacts with 21cm3 of 0.2 mol dm-3 HCl. calculate the molarity.

Ignore me, I was over-thinking the question (though it should say calculate the molarity of the sodium hydroxide)

The reaction is an acid + base = salt + water reaction.

First work out the balanced equation for NaOH and HCl ---> Salt + water

Then work out the moles of HCl present.

You can then calculate the number of NaOH in the reaction by multiplying the number of moles of HCl by the ratio NaOH to HCl which you calculated earlier.

This value is the number of moles of NaOH in 25cm3. To get to the answer you need to multiply that number so that it is in dm3.
Thank youuu!

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