normality

[pistolpete007]

What volume of 2 M H2SO4 is needed to neutralize 1L of a 5 N solution of Ca(OH)2

a.250 ml
b.625ml
c.800 ml
d.1200 ml
e. 2500 ml

i thought it was D becaus 2M x 2(b/c 2 H)(x)= 1000ml x 5 x 2 (b/c 2 OH)

and when i calculated this out i got 2500 ml
but the answer is 1200mL kaplan didnt take the 2OH's into account...can some1 tell me why is this?

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[bumpski20]

thats weird...i got 1250mL so im not pos this is right (unless they rounded but they didnt use the same amount of sig figs) but maybe this will help anyway:

2 M H2SO4 is needed to neutralize 1L of a 5 N solution of Ca(OH)2

the equation is M1v1=M2v2 right? so M of Ca(OH)2 = 2.5 (cuz of the 2 OH's). multiply that by 1L. divide that by 2M of the H2SO4 (you don't need to do anything to that cuz the M is already given) so it looks like (2.5M X1)/2 = 1.25L = 1250 mL

you can also do N1v1=N2v2 and it should equal the same. it will look like (5N X 1)/4 = 1.25L = 1250mL (is that what kaplan did?)

 

[kkatranji]

first of all I am very weak with Gchem so bear with me

Isn't Normality based on Acid Base properties in this case. So wouldn't 2 H in the H2SO4 counter the two OH's so that makes (2/2) or N=1.

I get confused with this stuff.

 

[DentalDeac]

The way I set it up, 2 M H2SO4 means that you have 2 moles of H2SO4 per liter. In the H2SO4 you have 2 mols of H+ for every mol of H2SO4, so there are 4 mols of H+ in 1 L of H2SO4.

In the 5M Ca(OH)2 you have 5 mol Ca(OH)2 and 2 mol of OH- per Ca(OH)2 for a total of 10 mol OH-. If you find an alternate explanation please let me know.

In order for the H+ to neutralize the OH- you would need 2500 mL. (4 x 2.5 L)

 

[vvvv]

What volume of 2 M H2SO4 is needed to neutralize 1L of a 5 N solution of Ca(OH)2

a.250 ml
b.625ml
c.800 ml
d.1200 ml
e. 2500 ml

i thought it was D becaus 2M x 2(b/c 2 H)(x)= 1000ml x 5 x 2 (b/c 2 OH)

and when i calculated this out i got 2500 ml
but the answer is 1200mL kaplan didnt take the 2OH's into account...can some1 tell me why is this?

You said 5N solution of Ca(OH)2 above, so Ca(OH)2 they already gave you normality you dont have to time 2. Only time 2 when they said 5M.

 

[Dencology]

yes.
i would say ans. is 1250. VVV said it. N is 5 so you don't need to multiply by 2 again. in reality it is 2.5M and since there is 2 OH- you get 5N.
hope this would work.

You said 5N solution of Ca(OH)2 above, so Ca(OH)2 they already gave you normality you dont have to time 2. Only time 2 when they said 5M.