Chem pst ppr ques....!!

[Muhammad Talha]

AOA...
plz anobody can solve n explain these questions:
June 06/P2/B9(b)
June 06/P2/B10....... :?:

 

[CaptainDanger]

Can you explain what you are not getting? There answers are clearly given in the marking scheme?

 

[Muhammad Talha]

Can you explain what you are not getting? There answers are clearly given in the marking scheme?

In B9 in the experiment i m cnfused with the titration and indicator thing....n i m nt able of being understand the next ques that is B10...

 

[CaptainDanger]

You mean why its repeated without the indicator thing the 2nd time? The reason for it is to make sure that the sample which comes at the end is pure...

Reagents required are HCl and KOH... When they react The KCl is formed.... You can use K2CO3 inplace of KOH... As the result would be the same...

Explanation:

A certain amount of KOH is added to a flask... Indicator here used can be phenolphthalein... HCl is added... And when the end point is reached the colour change would indicate that... It will become colourless... The amount of acid used is noted... And then the experiment is repeated again without indicator... After that the solution is evaporated or is left to dry to get the crystals of KCl...

 

[CaptainDanger]

Indicator used can be methyl orange too... For that the colour would become reddish or pink...

 

[CaptainDanger]

B10


a) Its alloy so the atoms won't slide over each other that easily... Thats the difference...

b) i-Blue colour... Zinc would give colourless solution, but as Copper is there so it masks that and gives a blue colour...
ii- Zinc Hydroxide and Copper Hydroxide are formed.... Again for copper the colour is blue... And for zinc white... Copper Hydroxide is insoluble in excess while zinc hydroxide will dissolve in excess of NaOH...

c) i- As Zinc is more reactive then Copper so Zinc Chloride is formed... And copper remains as a solid...
ii- Make the ionic equation for the reaction...

 

[Muhammad Talha]

Thank u very much.....

 

[CaptainDanger]

My pleasure....

 

[Muhammad Talha]

 

[CaptainDanger]

Have you read the forum RULES about signature?

 

[Muhammad Talha]

nup...y??

 

[CaptainDanger]

Animated images are not allowed... Plus your image is too big....

 

[Muhammad Talha]

Animated images are not allowed... Plus your image is too big....

Okk...no problem i will remove it....

 

[CaptainDanger]

Its so cute!

 

[Muhammad Talha]

 

[Muhammad Talha]

can u plz tell me the molecular formula of phosphorus(V) oxide...n how u derived it....

 

[leosco1995]

Phosphorous oxide contains only Phosphorous and oxygen (you can tell easily from the name). The (V) suggests that P has a charge of 5+. Oxygen has a charge of 2-. If you cross multiply them, you get P2O5. After checking it out on wikipedia, P2O5 is apparently the empirical formula but knowing the actual molecular formula being P4O10 is something I doubt would be asked in the paper.

 

[CaptainDanger]

I have seen a question asking for the empirical one I guess... Or they have not mentioned it there I guess.... Just says write the formula....

 

[Muhammad Talha]

Phosphorous oxide contains only Phosphorous and oxygen (you can tell easily from the name). The (V) suggests that P has a charge of 5+. Oxygen has a charge of 2-. If you cross multiply them, you get P2O5. After checking it out on wikipedia, P2O5 is apparently the empirical formula but knowing the actual molecular formula being P4O10 is something I doubt would be asked in the paper.

Thanx...In the marking scheme they hv said that both of them r correct....infact they hv asked for the molecular formula...

 

[Muhammad Talha]

I have seen a question asking for the empirical one I guess... Or they have not mentioned it there I guess.... Just says write the formula....

Here is the ques:-
What is the molecular formula of phosphorus(V) oxide?