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

A solution is obtained by mixing 300 g of 25% solution and 400 g of 40% solution by mass. Calculate the mass percentage of the resulting solution.

An antifreeze solution is prepared from 222.6 g of ethylene glycol (C₂H₆O₂) and 200 g of water. Calculate the molality of the solution. If the density of the solution is 1.072 g mL⁻¹, then what shall be the molarity of the solution?

A sample of drinking water was found to be severely contaminated with chloroform (CHCl₃) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass):

1. express this in percent by mass.
2. determine the molality of chloroform in the water sample.

If the density of some lake water is 1.25 g mL⁻¹ and contains 92 g of Na⁺ ions per kg of water, calculate the molality of Na⁺ ions in the lake.

If the solubility product of CuS is 6 × 10⁻¹⁶, calculate the maximum molarity of CuS in aqueous solution.

Calculate the mass percentage of aspirin (C₉H₈O₄) in acetonitrile (CH₃CN) when 6.5 g of C₉H₈O₄ is dissolved in 450 g of CH₃CN.

Nalorphene (C₁₉H₂₁NO₃), similar to morphine, is used to combat withdrawal symptoms in narcotic users. Dose of nalorphene generally given is 1.5 mg. Calculate the mass of 1.5 × 10⁻³ m aqueous solution required for the above dose.

Given the standard electrode potentials,

K⁺/K = −2.93 V, Ag⁺/Ag = 0.80 V,

Hg²⁺/Hg = 0.79 V

Mg²⁺/Mg = −2.37 V, Cr³⁺/Cr = −0.74 V

Arrange these metals in their increasing order of reducing power.

Depict the galvanic cell in which the reaction \[\ce{Zn(s) + 2Ag+(aq) → Zn^{2+}(aq) + 2Ag(s)}\] takes place. Further show:

1. Which of the electrode is negatively charged?
2. The carriers of the current in the cell.
3. Individual reaction at each electrode.

The decomposition of NH₃ on platinum surface is zero order reaction. What are the rates of production of N₂ and H₂ if k = 2.5 × 10⁻⁴ mol⁻¹ L s⁻¹?

The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:

Why is adsorption always exothermic?

Silver atom has completely filled d orbitals (4d¹⁰) in its ground state. How can you say that it is a transition element?

Explain giving reason:

Transition metals and many of their compounds show paramagnetic behaviour.

Write down the electronic configuration of Cr³⁺.

Write down the electronic configuration of Pm³⁺.

Write down the electronic configuration of Cu⁺.

Write down the electronic configuration of Ce⁴⁺.

Write down the electronic configuration of Co²⁺.

Write down the electronic configuration of Lu²⁺.