Is Matter Around Us Pure? — Science STD 9 — Question

Copper sulphate reacts with sodium hydroxide to form a blue precipitate of copper hydroxide and sodium sulphate. In an experiment, 15.95g of copper sulphate reacted with 8.0g of sodium hydroxide to form 9.75g of copper hydroxide and 14.2g of sodium sulphate. Which law of chemical combination is illustrated by this data? Give reason for your choice.

In what respects does a true solution differ from a colloidal solution?

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

Why is heat energy needed to melt a solid? What is this heat energy called?

In photosynthesis, 6 molecules of carbon dioxide combine with an equal number of water molecules through a complex series of reactions to give a molecule of glucose having a molecular formula C₆H₁₂O₆. How many grams of water would be required to produce 18g of glucose? Compute the volume of water so consumed assuming the density of water to be 1g cm^–3.

Calculate the molecular masses of the following:

1. Hydrogen, H₂
2. Oxygen, O₂
3. Chlorine, Cl₂
4. Ammonia, NH₃
5. Carbon dioxide, CO₂

(Atomic masses: H = 1 u; O = 16 u; Cl = 35.5 u; N = 14 u; C = 12 u)

You are provided with soda water, milk and muddy water. How can you differentiate between them in terms of:

1. Homogeneity.
2. Filtration.
3. Tyndall effect.

What are (i) metals (ii) non-metals, and (iii) metalloids? Give two examples each of metals, non-metals and metalloids.

Why does a desert cooler cool better on a hot dry day?