Chemistry MCQ thread...

[Zishi]

B

 

[hassam]

ya tru both b

 

[sweetiepie]

@ srukhan answer is C...50%

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

i hope itx clear to u..

 

[mickysharif]

ya tru both b

can you PLEASE explain why they boht are B...

 

[mickysharif]

Also..

 

[hassam]

in hydrolysis with NaOH of ester the products are alcohol and sodiu, salt of carboxylic acid....so ans here is B

 

[mickysharif]

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.

 

[hassam]

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

 

[mickysharif]

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?

 

[mickysharif]

 

[Hateexams93]

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

 

[Zishi]

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

 

[smartangel]

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

 

[Hateexams93]

can some1 plz answer to my question ((((((((((((((((((

 

[mickysharif]

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 ...=/

 

[Zishi]

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

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

 

[smartangel]

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..

 

[Xthegreat]

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

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.

 

[Zishi]

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

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...

 

[Hateexams93]

ohhhh -.-(blind me) ...didn't notice it ,thanx