Chemistry Practice Questions: pH Mixture and Gas Production

[Omm]

I am only a high school student so take some pity, I have an exam tomorrow and am trying to teach myself the method. But alas, not working >.<

Could someone please answer them for me with working? My teacher kind of rushed over this and I didnt really understand:

Q1) The pH of a mixture of 50ml or 0.4 M HCl and 50ml 0.4 Ba(OH)2 is closest to:

12.6
7.0
14.0
1.0

Q2) What volume of CO2 gas at 25*C and 101.3kPa is produced by the complete combustion of 4.0g of carbon in oxygen?

25.4L
12.7L
8.47L
4.24L

Please show working + formulas

Thanks a heap!

 

[QuarkCharmer]

Khan Academy has a really great series of videos about calculating weak/strong acid/bases. I recommend you check out that series of videos located here:
http://www.khanacademy.org/video/introduction-to-ph--poh--and-pkw?playlist=Chemistry

It's only about 30 minutes long and he does a great job explaining exactly how to solve these questions.

If you prefer, if you write out what you have worked the questions to so far, I will help you get to the desired result.

 

[Omm]

Thanks a heap! I will take a look at the video/s and see if I can get it :)

 

[Omm]

Yer, still having trouble. Could you please work the answer so I can see the process for 1?

EDIT: Ok I don't think there is like a formula or equation to follow for it? So it is just knowing that they both fully disassociate but Ba(OH)2 occupies more therefore it is basic. A pH of 14 in unreasonable with the HCl in the solution so by elimination it is 12.6?

 

[sjb-2812]

I am only a high school student so take some pity, I have an exam tomorrow and am trying to teach myself the method. But alas, not working >.<

Could someone please answer them for me with working? My teacher kind of rushed over this and I didnt really understand:

Q1) The pH of a mixture of 50ml or 0.4 M HCl and 50ml 0.4 Ba(OH)2 is closest to:

12.6
7.0
14.0
1.0

What happens when these two are mixed? acid + base -> ?

Q2) What volume of CO2 gas at 25*C and 101.3kPa is produced by the complete combustion of 4.0g of carbon in oxygen?

25.4L
12.7L
8.47L
4.24L

Please show working + formulas

Thanks a heap!

How many moles of CO₂ is formed by the combustion?

 

[Omm]

Answer to A is 12.6. Acid + Base --> Salt + Water however there is one H in HCL but two OH in Ba(OH)2 This will shift the pH to more basic.

I got it now as well as the CO2 produced. Thanks anyways.