Chemistry MCQ thread...

[Zishi]

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..

The answer is C.

It will 1 mole of Calcium nitrate will produce one moles of oxide.

Moles in 4.10 g = 4.10/{40+2[14+(16x3)]}

This will be moles of the oxide. Use moles = mass/Mr to find mass of oxide(as it is the only solid residue) formed.

 

[Hateexams93]

THESE R THE LAST QUESTIONS

help me plz

 

[histephenson007]

THESE R THE LAST QUESTIONS

help me plz

both answers are C?

 

[ShootingStar]

Analytical chemists can detect very small amounts of amino acids, down to 3 × 10^–21 mol.
How many molecules of an amino acid (Mr = 200) would this be?

A 9 B 200 C 1800 D 360 000

The answer is C, 1800.. I got the answer by multiplying (3 x 10^-21) by (6.02 x 10^23) .. but I'm not sure if my working is right? Can someone please confirm this..

 

[watscrackin]

@watscrackin answer is C
%yield = actual mass/calculated massx100
22/44x100
= 50%

i hope itx clear to u...

how is the calculated mass 44?

 

[xHazeMx]

THREAD CLOSED

 

[Mobeen]

really ?

 

[sweetiepie]

lol...

 

[anahita16]

hey..i need help in nov10/ variant 12, mcq no 18, 39 and 40.....

Q18 ans B
bromine is non polar so soluble in non polar (a is wrong)
it can easily vaporise( c is wrong)
in vapour state it is not purple (d is wrong)

I also thought so. Answer must be B but marking scheme says number 18 it's D! How can bromine vapour be purple? Iodine is purple, bromine is red brown! :%)
http://www.xtremepapers.me/CIE/Internat ... _ms_12.pdf

 

[rideronthestorm]

october november 06 question 4 ?

 

[Oliveme]

Please explain these questions? thanks very much
http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s10_qp_11.pdf
Questions 13, 28, 29.

 

[kimkimyap]

In a car engine, non-metallic element X forms a pollutant oxide Y.
Further oxidation of Y to Z occurs in the atmosphere. In this further oxidation, 1 mol of Y reacts
with ½ mol of gaseous oxygen.
What can X be?
1 carbon
2 nitrogen
3 sulfur

A. 1,2,3 B. 1,2 C. 2,3 D. 1

answer is C. can anyone please explain it by equation and why carbon cannot be the answer? Thanks.

 

[Monysa Adhikary]

Most modern cars are fitted with airbags. These work by decomposing sodium azide to liberate​

nitrogen gas, which inflates the bag.​

2NaN3
3N2 + 2Na​

A typical driver’s airbag contains 50 g of sodium azide.​

Calculate the volume of nitrogen this will produce at room temperature.​

A 9.2 dm3 B 13.9 dm3 C 27.7 dm3 D 72.0 dm3​

please help 2 make me clear if u think the answer is C

 

[bamteck]

Please someone help me for these 3 questions from June 02
Thanks

 

[thelearner]

 

[Monysa Adhikary]

What is the impact on extension when springs are kept vertical and horizantal?

 

[-Kaley-]

Please someone help me for these 3 questions from June 02
ThanksView attachment 15253

Q23 should be B. Convert the haloalkane to nitrile by adding KCN. Then add H2O to form carboxylic acid.
Q24 should be A as hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.
Q25 I think it is A. You can work it out by breaking the double bond at the 2nd C. It will bind with the CN- to form a chiral centre binding to H,O,C and CN.

Kindly correct me if there is any mistake

 

[-Kaley-]

Most modern cars are fitted with airbags. These work by decomposing sodium azide to liberate​

nitrogen gas, which inflates the bag.​

2NaN3
3N2 + 2Na​

A typical driver’s airbag contains 50 g of sodium azide.​

Calculate the volume of nitrogen this will produce at room temperature.​

A 9.2 dm3 B 13.9 dm3 C 27.7 dm3 D 72.0 dm3​

please help 2 make me clear if u think the answer is C

Moles of NaN3 = 50/(6*14+2*23)=0.385
Ratio = 2:3
Moles of N produced : 0.385/2*3=0.5775
Volume of N produced = 2(0.5775*24) = 27.7 (3s.f)

Kindly correct me if there is any mistake

 

[Varuna0911]

could you help me with Q14 june 2012 please

 

[Daniyal23]

Which Chlorine compound has bonding that can be described as ionic with some covalent character? A. NaCl B. MgCl2 C. ALCl3 D. SiCl4....The answer should be C right marking scheme say it is B?????