Class 11th

(i) During winter, the temperature of lake water keeps on decreasing. Since cold water is heavier, it moves towards the bottom.

(ii) Density of ice is less than that of water that is why it floats on the surface of water.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: The given reaction is :-

PCl5(g)?PCl3(g)+Cl2(g)

KC= $\frac{\left[\mathrm{P}\mathrm{C}\mathrm{l}3\right]\left[\mathrm{C}\mathrm{l}2\right]}{\left[\mathrm{P}\mathrm{C}\mathrm{l}5\right]}$

=1.2*10⁻³ *1.2*10⁻³ 0.8*10−3 $\frac{[1.2*10-3*1.2*10-3\mathrm{}]}{[0.8*10-3\mathrm{}]}$

=1.8*10⁻³molL⁻¹

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option (iii)

A physical equilibrium is having dynamic nature, both forward and reverse process occur at equal rates. Some kind of motion is always present. The individual molecules continuously move from one phase to another.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: option (iii)

A physical equilibrium is having dynamic nature, both forward and reverse process occur at equal rates. Some kind of motion is always present. The individual molecules continuously move from one phase to another.

This is a short answer type question as classified in NCERT Exemplar

(i) PBS (s)+4H₂O₂ (aq) → PbSO₄ (s)+4H₂O (l)

(ii) CO (g)+2H₂ (g) → CH₃OH (l)

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans: Option(iv)

 The given chemical reaction is:

H₂(g) + I₂(g) ? 2HI (g)

By, thermodynamical equation of equilibrium,

?G?= -RTlnk>0

Now, R>0 & T>0

⇒ −lnK > 0

⇒    K<1

This is a Multiple Choice Questions as classified in NCERT Exemplar

Ans:  Option(iv)

The relationship between Kp and Kc is

Kp=Kc(RT)Δn

Where ?n = (number of moles of gaseous products) – (number of moles of gaseous reactants)

For the reaction,

NH4C1(s)?NH3(g)+HCl(g)

Δn=2–0=2

This is a Short Answer Type Questions as classified in NCERT Exemplar

Ans:  Δ_rH^?= ?_fH? [CaO(s)]+ ?_fH?[CO2(g)]− ?_fH?[ [CaCO₃(s)]

∴ ?_fH? =178.3kJ mol⁻¹.

The reaction is endothermic. Hence, according to Le Chatelier's principle, reaction will proceed in forward direction on increasing temperature.

This is a short answer type question as classified in NCERT Exemplar

Ice has a highly ordered 3D hydrogen bonded structure. Each oxygen atom is surrounded tetrahedrally by four other oxygen atoms at a distance of 276 pm.

This is a Short Answer Type Questions as classified in NCERT Exemplar

Ans: As, NH₃ is Lewis base while BF₃  is Lewis acid. Lewis electronic theory of acids and bases explains it. Hybridisation state: N in NH₃ is sp³ hybridised and Boron in BF₃ is sp² hybridised.