[bhav406]

Calculate the molarity of the first named soultion.

25 cm³ of soduim hydroxide reacts with 21.0 cm³ of 0.2M HCL.

balanced equation = NaOH + HCL ------> NaCl + H2O



pls help me.....Bhav

[Borek]

How many moles of HCl? What molar ratio betwenn HCl and NaOH? How many moles of NaOH?

[lann]

Also, if you check your book, there should be a formula like this: M₁V₁ = M₂V₂
I think this formula relates to that question.

[Borek]

Also, if you check your book, there should be a formula like this: M₁V₁ = M₂V₂
I think this formula relates to that question.

No, it doesn't.

More precisely: it does, but only when there is 1:1 molar ratio. Don't use this formula blindly, or you will get into troubles.

[lann]

Also, if you check your book, there should be a formula like this: M₁V₁ = M₂V₂
I think this formula relates to that question.

No, it doesn't.

More precisely: it does, but only when there is 1:1 molar ratio. Don't use this formula blindly, or you will get into troubles.

Oops.  Sorry.  You are correct that it only works with 1:1 molar ratio.

But, you can include the ratio if you know how to use.
Ex. if it's 1:2 ratio, it would be M₁V₁(1/2) = M₂V₂
This method works for me.  Don't use it if you don't get it.  It's better to do the longer way (finding the moles, relating the moles, etc.)

[Borek]

I prefer not to mention this approach. Why? Because students instead of understanding that it is a shortcut think "Hey, that's the perfect and very simple way of dealing with titration problems! Why did they asked us to use these complicated methods?" and they forget that in fact it is all about stoichiometry and the reaction equation.

[lann]

I prefer not to mention this approach. Why? Because students instead of understanding that it is a shortcut think "Hey, that's the perfect and very simple way of dealing with titration problems! Why did they asked us to use these complicated methods?" and they forget that in fact it is all about stoichiometry and the reaction equation.

And, I'm one of those students. 
I did say to do the longest way to get there, instead.