Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Chemistry

Given below are two statements labelled as Assertion (A) and Reason (R).

Assertion (A): Alkyl halides are insoluble in water.

Reason (R): Alkyl halides have halogen attached to sp³ hybrid carbon.

Select the most appropriate answer from the options given below:

Assertion: Total number of octahedral voids present in unit cell of cubic close packing including the one that is present at the body centre, is four.

Reason: Besides the body centre there is one octahedral void present at the centre of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.

At high pressure the following reaction is zero order.

\[\ce{2NH3(g) ->[1130 K][Platinum catalyst] N2(g) + 3H2(g)}\]

Which of the following options are correct for this reaction?

(i) Rate of reaction = Rate constant.

(ii) Rate of the reaction depends on concentration of ammonia.

(iii) Rate of decomposition of ammonia will remain constant until ammonia disappears completely.

(iv) Further increase in pressure will change the rate of reaction.

Which of the following graphs is correct for a zero order reaction?

Write the rate equation for the reaction `2A + B -> C` if the order of the reaction is zero.

Derive an expression to calculate time required for completion of zero order reaction.

For a zero order reaction will the molecularity be equal to zero? Explain.

Which of the following curves is in accordance with Freundlich adsorption isotherm?

Freundlich adsorption isotherm is given by the expression `x/m = kp^(1/n)` which of the following conclusions can be drawn from this expression.

(i) When `1/n` = 0, the adsorption is independent of pressure.

(ii) When `1/n` = 0, the adsorption is directly proportional to pressure.

(iii) When n = 0, `x/m` vs p graph is a line parallel to x-axis.

(iv) When n = 0, plot of `x/m` vs p is a curve.

Which of the following statements is correct about the role of substances added in the froth floation process?

(i) Collectors enhance the non-wettability of the mineral particles.

(ii) Collectors enhance the wettability of gangue particles.

(iii) By using depressants in the process two sulphide ores can be separated.

(iv) Froth stabilisers decrease wettability of gangue.

In the Froth Floatation process, zinc sulphide and lead sulphide can be separated by:

(i) using collectors.

(ii) adjusting the proportion of oil to water.

(iii) using depressant.

(iv) using froth stabilisers.

Which of the following ores are concentrated by froth floation?

(i) Haematite

(ii) Galena

(iii) Copper pyrites

(iv) Magnetite

How do we separate two sulphide ores by Froth Floatation Method? Explain with an example.

Match items of Column I with the items of Column II and assign the correct code:

Match items of Column I with the items of Column II and assign the correct code:

Assertion: Sulphide ores are concentrated by Froth Flotation method.

Reason: Cresols stabilise the froth in Froth Flotation method.

In a cyclotrimetaphosphoric acid molecule, how many single and double bonds are present?

Why is nitric oxide paramagnetic in gaseous state but the solid obtained on cooling it is diamagnetic?

In the ring test of \[\ce{NO^{-}3}\] ion, \[\ce{Fe^{2+}}\] ion reduces nitrate ion to nitric oxide, which combines with  \[\ce{Fe^{2+} (aq)}\] ion to form brown complex. Write the reactions involved in the formation of brown ring.

\[\ce{P4O6}\] reacts with water according to equation \[\ce{P4O6 + 6H2O -> 4H3PO3}\]. Calculate the volume of 0.1 M NaOH solution required to neutralise the acid formed by dissolving 1.1 g of \[\ce{P4O6}\] in \[\ce{H2O}\].