KPK Board 12th class Chemistry Ch 19 Aldehydes and Ketones questions answers
We are providing all Students from 5th class to master level all exams preparation in free of cost. Now we have another milestone achieved, providing all School level students to the point and exam oriented preparation question answers for all science and arts students.
After Online tests for all subjects now it’s time to prepare the next level for KPK board students to prepare their short question section here. We have a complete collection of all classes subject wise and chapter wise thousands questions with the right answer for easy understanding.
We provided 12th class Chemistry short questions answers on this page of all KPK boards. Students of KPK boards can prepare the Chemistry subject for annual examinations.
In this List we have included all KPK boards and both Arts and Science students. These Boards students can prepare their exam easily with these short question answer section
Malakand Board 12th classes short questions Answer
Mardan Board 12th classes short questions Answer
Peshawar Board 12th classes short questions Answer
Swat Board 12th classes short questions Answer
Dera Ismail Khan Board 12th classes short questions Answer
Kohat Board 12th classes short questions Answer
Abbottabad Board 12th classes short questions Answer
Bannu Board 12th classes short questions Answer
All above mention KPK Boards students prepare their annual and classes test from these online test and Short question answer series. In coming days we have many other plans to provide all kinds of other preparation on our Gotest website.
How to Prepare KPK Board Classes Short Question Answer at Gotest
- Just Open the desired Class and subject which you want to prepare.
- You have Green bars which are Questions of that subject Chapter. Just click on Bar, it slides down and you can get the right answer to those questions.
- You can also Rate those question Answers with Helpful or not to make it more accurate. We will review all answers very carefully and also update time to time.
Now you can start your preparation here below
Aldehydes can be easily oxidized even by a mild oxidizing agent due to presence of hydrogen atom directly attached with carbonyl carbon. While no such hydrogen is there in all other carbonyl compounds this is characteristic hydrogen of aldehydes.
Nucleophilic addition reaction is a catalyzed by either by a acid or by a base,
Mechanism: In acid catalyzed addition reaction the addition process is initiated by the proton of the acid which combines with carbonyl oxygen atom to form oxonium ion. This increase the electrophilic nature of carbonyl carbon by inducing more positive charge on it and thus increase its ability to be attack by a weak nucleophiles.
In base catalyzed addition reaction the base react with attacking reagent and generate the nucleophile. This nucleophile attacked the carbon atom of carbonyl group and the pi electron of C=O bond move to the oxygen atom because of its high electronegativity.
Aldehydes and ketones undergo nucleophilic addition reactions whereas alkene,undergoes electrophilic addition reaction. This is because in case of aldehyde and ketones the =C=O bond is more polar due to greater electronegativity of oxygen atom which creates an electrophilic carbon therefore a nucleophile can easily attack the electrophilic carbon. Whereas double bond is alkene (C = C) is not that much polar due to which electron density is equally distributed between the two carbon atom hence an electrophile can be easily attacked hence they undergo electrophilic addition reactions easily rather than nucleophilic addition reaction.
Aldehydes can be easily oxidized because of presence of hydrogen atom directly attached with carbonyl carbon due to which an aldehyde can be easily oxidized as compare to ketone.
Ketones are less reactive than aldehydes towards nucleophile. The less reactivity of the ketones is due to the following two reasons;
- Steric Hindrance:
The carbonyl carbon of ketone is more crowded as compared to the aldehyde. Thus the approach of the nucleophile toward the positive charge carbon of carbonyl group is hindrance.
- Electronic effect of Alkyl group:
Another factor that decreases the reactivity of ketone is the electron donating effect of alkyl group attached to carbonyl carbon. Because alkyl group reduce the partial positive charge on carbonyl carbon.
The following two tests are used to distinguish between aldehydes and ketones.
(i) Tollen’s test (ii) Fehling Solution Test
1 Tollen’s Test:
CH3-CO-H + 2AgNO3 + NH4OH àCH3-CO—NH+4 + 2Ag + H2O
This test is not given by ketones.
(2) Fehling Solution Tests: Reagent: Cu(OH)2 / NaOH
CH3-CO-H + Cu(OH)2 + NaOH + CH3-CO–-Na+ + Cu2O + H2O
This test is also not given by ketones.