Question on Dehydration of Alkenes

What will the minor product be in the following reaction?

Question on Analytical Chemistry

Which one between (a) BaSO₄ and (b) BaCO₃ will be soluble in Hydrochloric Acid?

Question on Gaseous State

A gas is heated in such a way that its pressure and volume both becomes double. The temperature is then decreased. But, some additional air was taken in the container to maintain the volume and pressure which was doubled. If one-fourth of initial number of moles of air has been taken in for the purpose, what is the ratio of final temperature to the initial temperature?

Question on Wurtz Synthesis

Which one of the following cannot be prepared with high yield through Wurtz Synthesis?

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Question on Boiling Points

Which one of (a) Dimethyl ether (b) Ethanol and (c) Ethanal will have the highest boiling point?

Question on Acidic Strength

Which one of (a) Cl₂O₇ (b) SO₃ and (c) CO₂ is the strongest acid?

Question on Basic Strength & Nucleophilic Strength

Which one among is the strongest base and which one is the strongest nucleophile?
 (a) ^–CH₃ 
(b) ^–NH₂ 
(c) ^–OH 
(d) ^–F

Question on Dipole Moment

A poly atomic molecule having polar bonds will have non-zero dipole moment. Is this statement true or false?

Question on Carbocation Stability

Which one of the following two carbocations is most stable?

Question on Oxidation State

What is the oxidation state of Cr in CrO₅ molecule?

Question on Resonance Structures

Out of the two resonance structures (a) and (b) given for the compound (1), which one is the correct and stable resonance structure?

Question on Nomenclature

What is the IUPAC name of the simplest alkane (alkane with lowest molecular weight) which is optically active?

Answer:

3-methylhexane is the IUPAC name of the simplest alkane which is optically active.

Question on Stoichiometry

0.25 moles of sulphur was burnt to form SO₂ which is oxidised by Cl₂ water. The solution is treated with BaCl₂ solution. How many moles of BaSO₄ will precipitate?

Answer:

All the moles of sulphur taken initially will be present in the BaSO₄ precipitate. As one mole of BaSO₄ contains one mole of sulphur in it and 0.25 moles of sulphur (taken initially) will be present in it, 0.25 moles of BaSO₄ will precipitate.

Question on Reactive Rates

Alkenes react faster than comparable alkynes towards an electrophile under similar conditions. Is this statement true or false?

Answer:

The statement is true. The rate of a reaction depends on the stability of the intermediate. In the electrophilic addition reaction of alkenes & alkynes, carbocation is formed as an intermediate. The carbocation formed from an alkene is always more stable than that formed from an alkyne. So, alkenes react faster than comparable alkynes towards an electrophile under similar conditions.

Question on Molecular Formula

If the molecular formula for calcium pyrophosphate is Ca₂P₂O₇, which one of the following (a) Na₂P₂O₇ or (b) Na₄P₂O₇, will the molecular formula for sodium pyrophosphate be?

Answer:

Pyrophosphate ion (P₂O₇^4-) has four negative charges which are satisfied by two calcium ions (Ca²⁺). So, the molecular formula of sodium pyrophosphate will be Na₄P₂O₇.

Question on Electrophilic Strength

Which one of the two positions shown in the following molecule is most electrophilic?

Answer:

Carbon 1 is more electrophilic than Carbon 2. The positive charge on carbon 1 due to the presence of bromine atom and the carbonyl group is stabilized by inductive effect of the methyl group connected to it while the positive charge on the carbonyl carbon is stabilized by resonance from the lone pair of electrons from the oxygen atom of the alkoxy group connected to it. The stabilization due to resonance is superior compared to that of inductive effect. So, carbon 1 is more electrophilic than carbon 2.

Question on Potassium Permanganate

In which medium, (a) acidic (b) neutral and (c) basic does Potassium Permanganate act as the strongest oxidizing agent?

Answer:

In acidic medium a mole of potassium permanganate can accept 5 moles of electrons while in neutral and basic medium it can accept 3 and 1 moles of electrons respectively. So, potassium permanganate is the strongest as oxidizing agent in acidic medium.

Question on Nucleophilic Substitution

Out of the two compounds given below which one will undergo nucleophilic substitution faster? Why?

Answer:

There are couple of actors that affect the rate of nucleophilic substitution reactions. Here, the leaving group (halide ion) is the same and hence the electrophilic carbon can affect the rate of the reaction to a greater extent. In (a) the carbon connected to the bromine atom will tend to carry a negative charge because it having a negative charge will make the ring aromatic. In (b) the the carbon connected to the bromine atom will tend to carry a positive charge because it having a negative charge will make the ring aromatic. So, (b) undergoes nucleophilic substitution faster than (a).

Question on Molarity

What is the molar concentration of water?

Answer:

Molar concentration is the number of moles of the solute present in one litre of the solution. Taking the density of water to be 1g/mL, we can say that 1000mL of water weighs 1000g. 1000g of water has (1000/18) = 55.56 moles of water. Thus 1L of water contains 55.56 moles of it. So, the molar concentration of water is 55.56M.

Question on Isomerism

Consider the following two structures;

Is the relationship between the two structures (a) resonance or (b) tautomerism?

Answer:

It is Tautomoerism. Resonance involves only the movement of charge and does not involve the movement of atoms.