English Medium Class 9 - CBSE Question Bank Solutions

What is meant by atomicity ? Explain with two examples.

What is the atomicity of the following ?

1. Oxygen
2. Ozone
3. Neon
4. Sulphur
5. Phosphorus
6. Sodium

Write the formulae of the following compounds. Also name the elements present in them.

1. Water
2. Ammonia
3. Methane
4. Sulphur dioxide
5. Ethanol

In what form does oxygen gas occur in nature ?

In what form do noble gases occur in nature?

What do the following denote ?

1. N
2. 2N
3. N₂
4. 2N₂

What is the difference between the molecule of an element and the molecule of a compound? Give one example of each.

One of the forms of a naturally occurring solid compound P is usually used for making the floors of houses. On adding a few drops of dilute hydrochloric acid to P, brisk effervescence are produced. When 50 g of reactant P was heated strongly, than 22 g of a gas Q and 28 g of a solid R were produced as products. Gas Q is the same which produced brisk effervescence on adding dilute HCl to P. Gas Q is said to cause global warming whereas solid R is used for white-washing.

1. What is (i) solid P (ii) gas Q, and (iii) solid R.
2. What is the total mass of Q and R obtained from 50 g of P ?
3. How does the total mass of Q and R formed compare with the mass of P taken ?
4. What conclusion do you get from the comparison of masses of products and reactant ?
5. Which law of chemical combination is illustrated by the example given in this problem ?

Work out the formula for magnesium hydrogencarbonate.

What are (i) ionic compounds, and (ii) molecular compounds ? Give two examples of each type of compounds.

The cation of an element has :

Molecular compounds are usually formed by the combination between :

An element A forms an oxide A2O5.

What is the valency of element A ?

An element X forms the following compounds with hydrogen, carbon and oxygen :

H₂X, CX₂, XO₂, XO₃

State the three valencies of element X which are illustrated by these compounds.

Calculate the mass of 3.011 × 1024 atoms of carbon.

A student heats a beaker containing ice and water. He measures the temperature of the content of the beaker as a function of time. Which of the following (Fig. 1.1) would correctly represent the result? Justify your choice.

Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations.

A glass tumbler containing hot water is kept in the freezer compartment of a refrigerator (temperature < 0°C). If you could measure the temperature of the content of the tumbler, which of the following graphs (Fig.1.2) would correctly represent the change in its temperature as a function of time.

Conversion of solid state to liquid state is called fusion; what is meant by latent heat of fusion?

It is a hot summer day, Priyanshi and Ali are wearing cotton and nylon clothes respectively. Who do you think would be more comfortable and why?