• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Chemistry MCQ thread...

Messages
4,291
Reaction score
6,457
Points
523
@ srukhan answer is C...50%

%yield = actual mass/calculated massx100
22/44x100
= 50%

i hope itx clear to u..:)
 
Messages
2,619
Reaction score
293
Points
93
in hydrolysis with NaOH of ester the products are alcohol and sodiu, salt of carboxylic acid....so ans here is B
 
Messages
32
Reaction score
0
Points
16
I keep forgetting CO2C is ester =/ ...anyhow thanks.

Can you please help explain the other two you posted, which both have the answer B..

I totally don't get how it be 3 moles of HBr wouldn't it just take 2 moles?

and damn the solubility ones was soo annoying.
 
Messages
2,619
Reaction score
293
Points
93
see Br cn also undergo an SN1 reaction to replace OH....will solubility....one with most no. of h BONDS WILL HAVE HIGHEST SOLUBI.LITY
 
Messages
32
Reaction score
0
Points
16
OK I get the solubility one now and I understand that it can react molecules of HBr, but won't it also react with D, the oxidizing agent?
 
Messages
286
Reaction score
4
Points
0
Which statements about the reaction of solid sodium bromide with concentrated sulfuric acid are
correct?
1 Hydrogen bromide is a product of the reaction.
2 Sulfuric acid is oxidised to sulfur dioxide.
3 Bromide ions are reduced to bromine.
WHY 2 AND 3 ARE WRONG ? some plz tell me the reason :eek:
 
Messages
347
Reaction score
17
Points
28
please help me out on this one..

Use of the Data Booklet is relevant to this question.
Which mass of solid residue can be obtained from the thermal decomposition of 4.10 g of
anhydrous calcium nitrate?
A 0.70 g B 1.00 g C 1.40 g D 2.25 g
 
Messages
32
Reaction score
0
Points
16
Zishi said:

No, that's a tertiary alcohol group in it - they ain't oxidised.

I thought the C=C would get -OH attached like oxidation of alkenes, but guess not...Thanks. Best of luck for your exams.

At least I know which thread to look at when I'm retaking the exam ...=/
 
Messages
772
Reaction score
149
Points
38
Hateexams93 said:
Which statements about the reaction of solid sodium bromide with concentrated sulfuric acid are
correct?
1 Hydrogen bromide is a product of the reaction.
2 Sulfuric acid is oxidised to sulfur dioxide.
3 Bromide ions are reduced to bromine.
WHY 2 AND 3 ARE WRONG ? some plz tell me the reason :eek:

2 and 3 ain't wrong. I guess that You didn't see Mark scheme carefully.
 
Messages
347
Reaction score
17
Points
28
smartangel said:
please help me out on this one..

Use of the Data Booklet is relevant to this question.
Which mass of solid residue can be obtained from the thermal decomposition of 4.10 g of
anhydrous calcium nitrate?
A 0.70 g B 1.00 g C 1.40 g D 2.25 g

please answer my question..its almost time for the exam..
 
Messages
153
Reaction score
6
Points
0
Zishi said:
Hateexams93 said:
Which statements about the reaction of solid sodium bromide with concentrated sulfuric acid are
correct?
1 Hydrogen bromide is a product of the reaction.
2 Sulfuric acid is oxidised to sulfur dioxide.
3 Bromide ions are reduced to bromine.
WHY 2 AND 3 ARE WRONG ? some plz tell me the reason :eek:

2 and 3 ain't wrong. I guess that You didn't see Mark scheme carefully.

2 and 3 are wrong. sulphuric acid is not oxidised, it is a oxidising agent, it should be REDUCED
bromide ions are OXIDISED to bromine. 1- to 0.
 
Messages
772
Reaction score
149
Points
38
Xthegreat said:
Zishi said:
Hateexams93 said:
Which statements about the reaction of solid sodium bromide with concentrated sulfuric acid are
correct?
1 Hydrogen bromide is a product of the reaction.
2 Sulfuric acid is oxidised to sulfur dioxide.
3 Bromide ions are reduced to bromine.
WHY 2 AND 3 ARE WRONG ? some plz tell me the reason :eek:

2 and 3 ain't wrong. I guess that You didn't see Mark scheme carefully.

2 and 3 are wrong. sulphuric acid is not oxidised, it is a oxidising agent, it should be REDUCED
bromide ions are OXIDISED to bromine. 1- to 0.

Oh, I guess I read it as Sulfuric acid is reduced to sulfur dioxide....Yes 2 and 3 are wrong...
 
Top