Is Matter Around Us Pure — Science STD 9 — Question

Explain why, ice at 0°C is more effective in cooling than water at the same temperature.

How will you separate water from mustard oil?

Calculate the number of moles present in a drop of chloroform (CHCl₃) weighing 0.0239g.
(Atomic masses: C = 12u; H = 1u; Cl = 35.5u)

During an experiment the students were asked to prepare a 10% (Mass/ Mass) solution of sugar in water. Ramesh dissolved 10g of sugar in 100g of water while Sarika prepared it by dissolving 10g of sugar in water to make 100g of the solution.

1. Are the two solutions of the same concentration.
2. Compare the mass % of the two solutions.

How would you obtain sodium chloride from a mixture of sodium chloride and sulphur without using water?

An element X has a mass number = 37 and it contains 17 protons.

1. Write the symbolic representation of the element.
2. Find the number of neutrons and electrons in the element.
3. Write the electronic configuration of the element.

Comment upon the following:
Rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.

In an experiment, 1.288g of barium sulphate was obtained from 1.03g of barium. In another experiment, 3.672g of barium sulphate gave, on reduction, 2.938g of barium. Show that these figures verify the law of constant proportions.

When a gas jar containing air is inverted over a gas jar containing bromine vapour, the red-brown bromine vapour diffuse into air. Explain how bromine vapour diffuse into air.

Show by means of calculations that 5 moles of CO₂ and 5 moles of H₂O do not have the same mass. How much is the difference in their masses?