Cssa chemistry 2012 (3 Viewers)

[bec_12]

Hey, can anyone help me with this question?

Calculate the pH of the resulting solution when 25.0mL of 0.750 mol/Lhydrochloric acid solution is added to 10.0 mL of 0.500 mol/L of barium hydroxide solution???
Thanks!!!!

 

[Kimyia]

Hey, can anyone help me with this question?

Calculate the pH of the resulting solution when 25.0mL of 0.750 mol/Lhydrochloric acid solution is added to 10.0 mL of 0.500 mol/L of barium hydroxide solution???
Thanks!!!!

Do you have the answer?

 

[bec_12]

yes it was a multiple choice question
options are:
a) 0.456

b) 0.602

c) 1.862

d) 2.058

answer was B in the end

 

[Kimyia]

yes it was a multiple choice question
options are:
a) 0.456

b) 0.602

c) 1.862

d) 2.058

answer was B in the end

Do you still need help with it, or did you get it?

 

[bec_12]

still need help. did you manage to work it out?

i got this far:

2HCl + Ba(OH)₂ --> BaCl₂ + 2H₂O
I know no. of moles for HCl is 0.01875mol

no. of moles for Ba(OH)2 is 0.005mol

i know the HCl is in excess but where do i go from here?

 

[Kimyia]

still need help. did you manage to work it out?

i got this far:

2HCl + Ba(OH)₂ --> BaCl₂ + 2H₂O
I know no. of moles for HCl is 0.01875mol

no. of moles for Ba(OH)2 is 0.005mol

i know the HCl is in excess but where do i go from here?

ok, your moles for HCl is right but its (OH)2 in Ba(OH)2 so its 0.005 x 2 = 0.01.
Then work out how many moles of H+ are present after all the OH are neutralised (that's just the difference between them) which is 0.00875.
Then work out the concentration of that H+ by dividing 0.00875 by 0.025 + 0.01 (the total volume). Then do your log Should give you 0.602.

 

[bec_12]

ok, your moles for HCl is right but its (OH)2 in Ba(OH)2 so its 0.005 x 2 = 0.01.
Then work out how many moles of H+ are present after all the OH are neutralised (that's just the difference between them) which is 0.00875.
Then work out the concentration of that H+ by dividing 0.00875 by 0.025 + 0.01 (the total volume). Then do your log Should give you 0.602.

yes it worked!! thankyou so much for your help

 

[Kimyia]

yes it worked!! thankyou so much for your help

no worries, sorry for not getting back to you sooner

 

[someth1ng]

I just think its stupid to try and stop people from sharing them.

Yeah, I wasn't being serious. Education should be free for all, not commercial like CSSA.

 

[yehhkate]

It's tommorrow.... SO SCARED!

 

[mandy moos zoo]

Me - how do I get them???

 

[t-razz]

LOL.. looking for answers and look what i come across!

 

[madharris]

Good luck guys

I'm sure you'll all do fine

 

[mrteeson]

Goodluck everyone, im pumped!!! Lets do this shit fightinggggggggggggg

 

[Brett_P]

This was a hard, hard assessment. I went really really bad.

God. Damn.

Goodbye top 5 rankings...

 

[habitres]

pretty easy.
Knew pretty much everything.
Last minute revision ftw. Lets see what mark i get (hoping 90+)
Some of the multiple choice was a bit odd.

 

[blieu]

Some of the multiple choice was a bit odd.

+1

 

[vinhkn]

Relatively easy paper, how'd everyone else find it. I got stumped by the 3rd multiple choice lol.

 

[tickleyouemo]

Relatively easy paper, how'd everyone else find it. I got stumped by the 3rd multiple choice lol.

same

 

[iampeterr]

pretty fair paper imo.