Chemistry MCQ thread...

[magnesium]

Fats and grease that build up on pans used in cooking are esters. Pans which are dirty from fats
or grease may be cleaned by heating them with a reagent that will react with the ester group.
What may be used to clean such pans by this reaction?
1 vinegar - aqueous ethanoic acid, CH3CO2H
2 alcohol - ethanol, C2H5OH
3 baking powder - sodium hydrogencarbonate, NaHCO3
HELP !!!!!!!!!!!!!!!!!!!!!! plzzzzzzz

 

[darknessinme]

Fats and grease that build up on pans used in cooking are esters. Pans which are dirty from fats
or grease may be cleaned by heating them with a reagent that will react with the ester group.
What may be used to clean such pans by this reaction?
1 vinegar - aqueous ethanoic acid, CH3CO2H
2 alcohol - ethanol, C2H5OH
3 baking powder - sodium hydrogencarbonate, NaHCO3
HELP !!!!!!!!!!!!!!!!!!!!!! plzzzzzzz

Acid hydrolysis so only 1 which is D i think

 

[sweetiepie]

Tips For 31-40 (Chemistry MCQ's Paper 1)

. If 1st choice is obviously incorrect, the answer is automatically C.
. If 2nd choice is obviously incorrect the answer is automatically D.
. If 3rd choice is incorrect and 2nd choice is correct the answer is B.
. If 1st choice and 3rd choice are right the answer is A.

hope this helps everyone

 

[Nagaanusan]

can u help me

 

[aalmuhannadi]

A question regarding the practicals; if, for example, you were doing a titration of some kind, and you just finished doing a rough titration. Then, when you are going to pour the conical flask containing the alkali and the pH indicator down the sink and prepare to refill it with the alkali and indicator solution again, do you wash the flask in between or just pour it down and fill it up with the alkali again for the second titration? If you do have to wash it, do you wash it with distilled water or normal tap water? And also, would you have to put some tissues down there and dry it or just wash it and pour the alkali in again immediately? Thanks help would be appreciated!

 

[Nagaanusan]

A question regarding the practicals; if, for example, you were doing a titration of some kind, and you just finished doing a rough titration. Then, when you are going to pour the conical flask containing the alkali and the pH indicator down the sink and prepare to refill it with the alkali and indicator solution again, do you wash the flask in between or just pour it down and fill it up with the alkali again for the second titration? If you do have to wash it, do you wash it with distilled water or normal tap water? And also, would you have to put some tissues down there and dry it or just wash it and pour the alkali in again immediately? Thanks help would be appreciated!

thanks

 

[KARLOTTAMAN]

Cl-35 + Cl-75 = Cl_2
where did u get Cl-75 from ?

ok for bromine how is it has 5 peaks explain

 

[Abhi Mevawala]

guyzz plzz hllp

 

[Abhi Mevawala]

one mre

 

[Abhi Mevawala]

hlp

 

[Abhi Mevawala]

hlp

 

[darknessinme]

guyzz plzz hllp

X has only Al and C in it. So all C in CO2 formed comes from the compound X.
n(CO2)=72/24000 mol, so that means m(CO2)=0.132g. From this fraction of C is 12/44 x 0.132g=m(C)=0.036g which is found in compound X.
So then m(Al)=0.132-0.036=0.108
From that you can work ratio of Al:C using method to find empirical formula. Ratio of Al:C turns out to be 4:3, so then answer is C which is the only multiple.

 

[Abhi Mevawala]

thnxx plzz try out the otheerzz

 

[Avik181]

6,7,8 please!!

 

[Ltzewei]

6,7,8 please!!

For 6, A would give 1p,2e,1n. B would be 11p,10e,8n. C gives 9p,10e,9n. D gives 9p,10e,8n
So the obvious answer would be D
For 7, 1 is 109.5 as it is a tetrahedral structure,2 is 120 because its a planar. 3 has a bent shape due to the 2 lone pair of electrons, making it 104. So the answer is C

For 8, I drew the Hess' law diagram to obtain delta H= [4(-394)+5(-286)] - [-2877] = -129, making it D

 

[Abhi Mevawala]

guyzz i hav many doubtzz uploaded here plzz try n solve it
https://www.xtremepapers.com/community/threads/chemistry-post-your-doubts-here.9859/page-336

 

[isa2hard]

is there a guide on how to do these multiple choice? srsly they are so hard i doubt i can even get 10/40

 

[isa2hard]

help pls

 

[Abhi Mevawala]

is the ans D for first one?
and C for second one
C because see the differene aftr 3rd ionisation energy its bigger so shell change therefor valancy is 3+ so ans is Xcl3

 

[geminisign]

Hi Would like some help for this question please. The answer says only 2 and 3 are correct. I do not understand why 1 is incorrect.

Which reagents, when used in an excess, can be used to make sodium lactate, CH3CH(OH)CO2Na, from lactic acid, CH3CH(OH)CO2H?
1 Na
2 NaHCO3
3 NaOH

Thanks!