How many moles of electrons will be released by one mole of dichloroacetic acid when it is converted to chlorine, carbon dioxide and water in a reaction?
Answer:
6 moles of electrons will be released by one mole of dichloroacetic acid in that reaction. The chlorine atoms will release 2 moles of electrons as their oxidation state changes from -1 to 0 and the carbon atoms will release 4 moles of electrons as their oxidation state changes from +2 to +4.
Which of the following compounds is the strongest nitrogen base and why?
Answer:
(3) is the least basic among the three as the nitrogen atom present in it is sp2 hybridised while the nitrogen atoms in (1) and (2) are sp3 hybridised. sp2 hybridised atom will have less tendency to donate electrons compared to an atom which is sp3 hybridised as the s-character in sp2 hybrid orbitals are more. Comparing (1) and (2) the availability of electrons in nitrogen atom in compound (2) will be decreased by the presence of oxygen atom in the molecule. So, (1) is the strongest nitrogen base as the availability of electrons are more on the nitrogen atom in that molecule.
When NaOH solution is added to an aqueous solution of Zinc Chloride, it produces a white precipitate which further dissolves on further addition of NaOH. Why?
Answer:
Zinc Chloride reacts with NaOH to produce a white precipitate of Zinc Hydroxide and on further addition to NaOH, forms a complex ion and hence dissoves.
ZnCl2 + 2NaOH = Zn(OH)2
Zn(OH)2 + 2NaOH = Na2[Zn(OH)4]
Zn(OH)2 is insoluble and Na2[Zn(OH)4] is soluble in water.
The values of Standard Reduction Potential for three metal ions A, B and C are 0.5, -3.0 and -1.2 respectively. Which corresponding metal among the three is the best reducing agent?
Answer:
Standard Reduction Potentials (SRPs) tell us about the potential that a metal ion has to get reduced while Standard Oxidation Potentials (SOPs) tell us about the potential that a metal has to get oxidised. SOP is same in magnitude but opposite in direction compared to SRP. From the given SRP values it is evident that metal ion B has the least SRP value. So, the metal B will be the one which will have the highest standard oxidation potential and hence act as the best reducing agent among the three metal ions.
How many P-O-P bonds are present in a molecule of P4O10 ?
Answer:
There are 6 P-O-P bonds in a molecule of P4O10.
Outline a mechanism to show how two molecules of methylpropene can react to form 2,4,4-trimethylpent-2-ene. (submitted by http://tothesky-flyinghigh.tumblr.com)
Answer:
Acetonitrile (MeCN) reacts with MeMgI followed by acid treatment to give acetone.
What will be the product when HCN is made to undergo the same sequence of reactions as above?
Answer:
Grignard Reagent is a source of aklyl carbanion which can behave as a base as well as a nucleophile. Also, Grignard reagent gets decomposed in presence of any acidic compound. In the given reaction methyl carbanion generated from the Grgnard reagent acts as a base and will abstract the proton from HCN and get decomposed as methane.
Which among the following two cations is the most stable?
Answer:
(2) is most stable among the two cations given because nitrogen atom is less electronegative than oxygen atom and hence will destabilize the positive charge on carbon atom to a lesser extent by inductive effect. Moreover, nitrogen atom will have more tendency than oxygen atom to provide the lone pair of electrons available with it for the resonance stabilization of the positive charge on the carbon atom.
Why is an aqueous solution of sodium acetate alkaline?
Answer:
Acetate ion gets hydrolyzed in the aqueous solution to produce hydroxide ions.
AcO- + H2O = HOAc + HO-
This increases the concentration of hydroxide ions in the solution and as a result the solution becomes alkaline.
If the half life of a first order reaction is 120sec, how long would it take for the reaction to be 90% complete?
Answer:
The rate constant (k) = 0.693/120 = 5.775 * 10-2 sec-1
The time taken for 90% completion is
t = (2.303/5.775 * 10-2) * log (100/10) = 398.78 sec
What will be the ratio between the root mean square velocity of H2 at 50 K and that of O2 at 800 K?
Answer:
Root Mean Square Velocity = sqrt(3RT/M)
Hence, sqrt(3R * 50 / 2) / sqrt(3R * 800 / 32) = 1
Which of the following hydroxides get replaced first by iodide ion in the following reaction?
Answer:
(1) will get replaced as the carbocation formed in that position will be stabilized by resonance while the carbocation formed at other positions will be stabilized by inductive effect.
What is isoelectric point for an amino acid?
Answer:
Amino Acids exists in the dipolar ionic form known as the “Zwitter” ions. This dipolar ionic form can behave as a base as well as an acid.
In the above reaction scheme (B) is the dipolar ion, (A) is the conjugate acid of the dipolar ion and (B) is the conjugate base of the dipolar ion. In an solution of amino acids all the three forms will be existing.
It is evident that as the solution becomes basic the equilibrium will shift forward and as the solution becomes acidic the equilibrium will shift backward. So, depending on the pH of the solution there will be either an excess concentration of (A) or (B). There will be a particular pH at which the concentrations of both (A) and (B) are equal. That pH is called the isoelectric point for an amino acid.
Which is the only primary alcohol that shows positive Iodoform Test?
Answer:
Iodoform Test is used to identify the presence of the following two groups.
The only primary alcohol that fulfills the structural requirement to show positive iodoform test is ethyl alcohol.
How many moles of carbonyl groups will be obtained on reductive ozonolysis of one mole of isoprene?
Answer:
The answer is 4. The products of reductive ozonolysis of one mole of isoprene are two moles of formaldehyde and a mole of 2-keto poranal.
When equal volumes of two solutions, one with pH = 2 and the other with pH = 1 are mixed, what will be the pH of the resulting solution?
Answer:
As both the solutions have the pH values as 1 and 2 we can conclude that they are acidic solutions. Let us call the solution with pH = 1 as A and that with pH = 2 as B.
The total H+ concentration from solution A is 10-1 and that from the solution B is 10-2.
Let 10mL of both the solutions be added (the actual volume does not make any difference in the pH of the final solution).
Millimoles of H+ from solution A = 10-1 * 100
Millimoles of H+ from solution B = 10-2 * 100
Total millimoles of H+ in the final solution is (10-1 * 100) + (10-2 * 100)
The total concentration of H+ in the final solution is ((10-1 * 100) + (10-2 * 100))/200 = 11/200 = 5.5 * 10-2 mol/L
So, the pH of the final solution is –log (5.5 * 10-2) = 2 – log5.5 = 1.26
Out of (i) 2-methyl butanioc acid and (ii) 3-methyl butanoic acid, which one is optically active?
Answer:
One simple way to find out if an organic molecule is optically active or not is to check for the chiral carbon (a carbon whose valancies are satisfied by 4 different groups).
2-methylbutanoic acid has a chiral carbon and is optically active.
50mL of 0.1M Sulphuric Acid solution was mixed with 50mL of 0.1M Barium Hydroxide solution. The rise in temperature of the mixture was found to be T1. Will the rise in temperature of the mixture be (1) equal to T1 or (2) more than T1 or (3) less than T1, if 100mL of both the solutions of same concentrations are mixed?
Answer:
The enthalphy of neutralization is the amount of heat released when one equivalent of and acid is neutralized with one equivalent of a base. It is a constant and at 298K its value is -57.3 kJ/mol.
Sulphuric acid is a dibasic acid and Barium Hydroxide is a diacidic base. So, equal moles of them is also same as equal equivalents. In the first case 5 millimoles (or equivalents) of both the acid and base are mixed. This neutralization reaction will release some amount of heat which will be used to increase the temperature of 100mL of the solution. In the second case 10 millimoles (or equivalents) of both the acid and the base are mixed. This neutralization reaction will release twice the amount of heat released in the first case but will now be used to increase the temperature of 200mL of the solution.
In both the cases, the heat per mL of the solution is the same and hence temperature rise will also be the same and equal to T1.