Chem Questions

[doboman]

hey guys, (mao-lol), i was just wondering if i can get some help on the following questions:

VCAA 2005 exam 1/Qn 5 and 13.

Explaination would be appriciated, thanks

[Collin Li]

I assume you mean the multiple choice questions.

Link: VCAA 2005 Exam 1


Question 5
0.10 mole of reacts completely with molecular oxygen, . Find the number of mole of oxygen molecules used.

Write a balanced combustion reaction between the fuel (butanol) and oxygen:






Question 13
20.0 mL of 0.10 M hydrochloric acid (HCl) reacts with 20.0 mL of 0.30 M potassium hydroxide (KOH) solution. Find the concentration of potassium ions in the resultant solution, in mole per litre.



The potassium ions don't react at all - an acid-base reaction will take place, consuming the and species, but the other ions will just float around in solution as spectator ions. So the number of mole of potassium ions will remain 0.0060.

However, the volume has changed. A 20.0 mL solution was added to a 20.0 mL solution, so now there are 40.0 mL. The concentration of the potassium ions must be:

[doboman]

thanks, it was just very confusing. So did we find out that the K+ions didnt react because they were in excess?

[Mao]

no, K⁺ are spectator ions, they do not react at all. they just, "hang around"

the actual ionic equation is:



which does not involve the K⁺ nor the Cl^-.


and btw, why "mao-lol"??

[doboman]

you seem to be the quickest to answer all chem questions...Cob beat you to it tho

[Mao]

no wai, coblin is easily the fastest ninja around (when he's around), and way more knowledgeable than myself