chem 2008 q's..

[khalil]

Q5 ii...

it asks for the functional group on the side chain of serine....

does that mean the Z group... which includes ch2 0H .. but the answer on says hydroxy.... so does that mean ch3, ch2,, ect.. can't be classified as functional groups?? but don't they influence the properties of the organic compound

[TrueTears]

Notice the question, it says "what's the functional group ON the SIDE CHAIN of serine"

You are correct in saying the side chain is

But the question didn't just ask for the SIDE CHAIN, it asks for the functional group OF the side chain. Hence the functional group of is just plain (hydroxy)

[khalil]

ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

thx for that.... but  can a branch e.g methane be considered as a functional group?

[TrueTears]

No, only methyl functional group can be.

[khalil]

54 g of zinc metal is completely dissolved in 250 mL of concentrated hydrochloric acid to give gaseous hydrogen according to the equation
Zn (s) + 2 HCl (aq)  ZnCl2 (aq) + H2 (g)

The concentration of zinc ions in the solution after all the zinc has reacted would be
a.   0.10 M
b.   0.20 M
c.   0.40 M
d.   0.025 M

someone help please

[Over9000]

Maybe multiply by 100?

[khalil]

Question 10
15.0 mL of 0.100 M iron (III) nitrate (Fe(NO3)3) reacts with 25.0 mL of 0.150 M potassium hydroxide (KOH). The maximum mass, in gram, of iron (III) hydroxide (Fe(OH)3) that can be precipitated from the reaction is
a.   0.133
b.   0.160
c.   0.400
d.   0.481

[khalil]

Question 12
What volume of water, in millilitres, must be added to 30 mL of 10 M ammonia solution in order to make a 0.50 M solution of ammonia?
a.   120
b.   150
c.   570
d.   600

Question 13
When water is added to a dilute solution of NH3 (aq), the pH of the solution
a.   rises and its percentage dissociation increases
b.   falls and its percentage dissociation increases
c.   rises and its percentage dissociation decreases
d.   falls and its percentage dissociation decreases

[Mao]

Q12,

hence 570 mL of water must be added to the 30 mL

Q13, actually this falls in the 'equilibrium' section of the course in unit 4. The answer is b, a dilution always cause the solution to go more 'neutral', in this case, NH3 is a base --> falls towards 7. Percentage dissociation also increases as water is a reactant in the equation

[khalil]

thanks mao!

Item 9
The mass of poly(ethylene) that could be produced from 250 L of gaseous ethylene (relative molecular
mass of ethylene = 28) at 20.0°C and 1000 kPa is
A. 4.21 x 107 g
B. 2.87 x 106 g
C. 4.21 x 104 g
D. 7.87 x 103g

[Mao]

pV=nRT, using the information given, you can work out the number of moles of ethylene (aka ethene)

since ethene undergoes addition polymerisation (no waste products), the mass of polyethylene is simply the mass of reactants you start with, i.e. n*Mr

[khalil]

Yer I did that but didnt get the correct answer...could u work it out?

[chem-nerd]

Q10 
KOH is your limiting reagent so you should get answer A

Item 9
are you sure you've typed this question correctly? I think the answer is B but it's out by a factor of 1000

Which exams/books are you getting these questions from?

[khalil]

i got it from BoS 1993 exam

[khalil]

IR spectroscopy is an analytical tool often used in organic chemistry. Which of the following
could be distinguished from the other molecules due to the absence of a particularly distinct
and characteristic peak?
(a) CH3CH2CH2CH2OH
(b) CH3CH2CH2COOH
(c) CH3CH2CH2CH2NH2
(d) CH3CH2CH2COOCH3