Science (English Medium) Class 12 - CBSE Question Bank Solutions for Chemistry

How is the sign of Δ_mixH related to positive deviations from Raoult’s law?

Heptane and octane form an ideal solution. At 373 K, the vapour pressures of the two liquid components are 105.2 kPa and 46.8 kPa respectively. What will be the vapour pressure of a mixture of 26.0 g of heptane and 35 g of octane?

Suggest the most important type of intermolecular attractive interaction in the following pair.

acetonitrile (CH₃CN) and acetone (C₃H₆O)

Vapour pressure of pure acetone and chloroform at 328 K are 741.8 mm Hg and 632.8 mm Hg respectively. Assuming that they form ideal solution over the entire range of composition, plot `p_"total"`, `p_"chloroform"` and `p_"acetone"` as a function of `chi_"acetone"`. The experimental data observed for different compositions of mixtures is:

Plot this data also on the same graph paper. Indicate whether it has a positive  or negative deviation from the ideal solution.

If a current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons would flow through the wire?

Suggest a list of metals that are extracted electrolytically.

Consider the reaction: \[\ce{Cr2O^{2-}_7 + 14H^+ + 6e^- -> 2Cr^{3+} + 7H2O}\]

What is the quantity of electricity in coulombs needed to reduce 1 mol of  \[\ce{Cr2O^{2-}_7}\]?

How much charge is required for the following reduction:

1 mol of Al³⁺ to Al?

How much charge is required for the following reduction? 

1 mol of Cu²⁺ to Cu.

How much charge is required for the following reduction:

1 mol of \[\ce{MnO^-_4}\] to Mn²⁺?

A solution of Ni(NO₃)₂ is electrolysed between platinum electrodes using a current of 5 amperes for 20 minutes. What mass of Ni is deposited at the cathode?

Three electrolytic cells A, B, C containing solutions of ZnSO₄, AgNO₃ and CuSO₄, respectively, are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper and zinc were deposited?

Why is the ester hydrolysis slow in the beginning and becomes faster after sometime?

What are enzymes? Write in brief the mechanism of enzyme catalysis.

Name the processes from which chlorine is obtained as a by-product.

Explain on the basis of valence bond theory that [Ni(CN)₄]²⁻ ion with square planar structure is diamagnetic and the [NiCl₄]²⁻ ion with tetrahedral geometry is paramagnetic.

Predict the number of unpaired electrons in the square planar [Pt(CN)₄]²⁻ ion.

Discuss the nature of bonding in the following coordination entity on the basis of valence bond theory:

[Fe(CN)₆]⁴⁻

[Cr(NH₃)₆]³⁺ is paramagnetic while [Ni(CN)₄]²⁻ is diamagnetic. Explain why?

Discuss the nature of bonding in the following coordination entity on the basis of valence bond theory:

[FeF₆]³⁻