Chemistry MCQ's help!

[bikermicefrmars]

Chem Nov 2005 paper 1 Q.5:

Which two gases each change the colour of damp red litmus paper?
A ammonia and chlorine
B ammonia and hydrogen chloride
C carbon dioxide and chlorine
D carbon dioxide and sulphur dioxide

Marking scheme say its answer is A. But I dont think so because from what I know Ammonia turns most red litmus blue BUT CHLORINE TURNS BLUE LITMUS PAPER RED AND BLEACHES IT.....so chlorine shouldn't be doing anything to red litmus!??

 

[bikermicefrmars]

This one as well:
Q What is the mass of aluminium in 204 g of aluminium oxide, Al2O3?
A 26 g B 27 g C 54 g D 108 g

Answer: D

And this one:
Q Hydrogen can form both ionic and covalent compounds.
With which element will hydrogen form an ionic compound?
A carbon
B chlorine
C nitrogen
D sodium

Answer

And from which chaps are these questions?

 

[bikermicefrmars]

Waiting!

 

[InshallahAajaega]

ok!
just a sec

 

[InshallahAajaega]

the answer of the first question is ammonium and hydrogen chloride!!!
hydrogen chloride also turns moist blue litmus red!!!
and and the ans of the aluminium oxide question is :
first we calculate the Mr of aluminium in the compound in this case its 27x2 = 54
next we calc. the Mr of the entire compound which is 54 +(16x3)= 102
we divide both as in 102/54 = 1.889
and finally multiply this value to the given mass i.e 204 x 1.888889 = 108
and thts ur answer !!!

 

[abcde]

The second question has been answered correctly by inshallahaajaega. BUt you're wrong at the first one. Chlorine is an acidic gas and turns moist blue litmus paper red and then bleaches it so A is correct. Hydrogen forms an ionic compound with sodium.

 

[InshallahAajaega]

o wait ur rite!!!
but chlorine turns blue litmus to red
the question says which gas changes the colour of blue litmus :/

 

[bikermicefrmars]

But @abcde.....if chlorine turns blue litmus red it shouldn't be doin anything to red litmus!!

And what abut 3rd question?

 

[InshallahAajaega]

xactly my point !!!
and sorry fr tht mstake!!!
2/3 aint bad !!!

 

[InshallahAajaega]

ans of third question is sodium !!!

 

[abcde]

Like I've mentioned before, chlorine turns moist blue litmus paper red, then BLEACHES it. Remember, chlorine is an acidic gas AND a bleaching agent. Hope this clears it up.

 

[bikermicefrmars]

In question no.3....hydrogen and sodium are both metals so how will they form ionic compound? Shouldn't the answer by Chlorine?

 

[InshallahAajaega]

did u just say tht hydrogen is a metal ??????????????????

 

[InshallahAajaega]

@abcde
yar the question says k wich gas shud chnge color of a RED litmus paper !!! u answrd tht chlorine changes the color of a BLUE litmus paper to red!!!

 

[leosco1995]

Chlorine does not change the color of litmus to red, it bleaches it and changes the color of it to white.

 

[bikermicefrmars]

From what I know hydrogen can exist as a metal, non-metal and ion. But is placed in Alkaili Metals.....so I was a bit confused!

 

[bikermicefrmars]

Another One:

Q A student tested a solution by adding aqueous sodium hydroxide. A precipitate was not seen
because the reagent was added too quickly.
What could not have been present in the solution?
A Al3+ B Ca2+ C NH4+ D Zn2+

Shouldn't the answer be NH4+?

 

[scouserlfc]

This one as well:
Q What is the mass of aluminium in 204 g of aluminium oxide, Al2O3?
A 26 g B 27 g C 54 g D 108 g

Answer: D

And this one:
Q Hydrogen can form both ionic and covalent compounds.
With which element will hydrogen form an ionic compound?
A carbon
B chlorine
C nitrogen
D sodium

Answer

And from which chaps are these questions?

well Q1 on this is from stochiometry and q2 is from bonding.

Well the bond mentioned in Q2 here is of dative covalent bond although it is not in the syllabus you guys should read it as it will help u in the A'Level as well here is the link. http://www.chemguide.co.uk/atoms/bonding/dative.html

The answer is not D it is Chlorine HCl is formed by ionic bonding of hydrogen and chlorine, use the link and you will see how it is bonded but if u dont understand please ask dont hesitate.


Here the answer for the first question is D so hope you get it. Well i used proportion method

so here is my working. (27+27)/102 * 204 = 108g hope u understand this working

 

[InshallahAajaega]

Chlorine does not change the color of litmus to red, it bleaches it and changes the color of it to white.

yar it chnges the color of BLUE litmus to white !!!!!
the hell do u keep on sayin tht it bleachs it????????

 

[screamingskull]

because it does bleach it!