Changes,Reactions and Recap

Q. What is the correct chemical equation for the combustion of charcoal (carbon) in the presence of oxygen?

1. $C\left(g\right)+O_2\left(g\right)\to {\mathrm{CO}}_2\left(g\right)$
2. $C\left(s\right)+O_2\left(g\right)\to {\mathrm{CO}}_2\left(g\right)$
3. $C\left(s\right)+2O\left(g\right)\to {\mathrm{CO}}_2\left(g\right)$
4. $C\left(g\right)+2O\left(g\right)\to {\mathrm{CO}}_2\left(g\right)$

Q.

A chemical reaction does not involve:

1. Formation of new substances having entirely different properties than that of the reactants.

2. Breaking of old chemical bonds and formation of new bonds.

3. Rearrangement of atoms of reactants to form new products.

4. Changing of the atoms of an element into those of another element to form new products.

Q. What is the chemical formula of magnesium nitride?

1. $M{g}_3{N}_2$
2. $N_{2}M{g}_3$
3. $M{g}_2{N}_3$
4. $M{g}_4{N}_3$

Q.

State true and false, mass is not conserved during a chemical reaction.

1. True

2. False

Q.

Rusting of an article made up of iron is called

1. corrosion and it is a physical as well as chemical change

2. dissolution and it is a physical change

3. corrosion and it is a chemical change

4. dissolution and it is a chemical change

Q.

Rolling of chapatti is an example of physical change and baking of chapatti is an example of _______ change.

1. Physical

2. Chemical

3. Both physical & chemical

4. Periodic

Q.

An artist made a statue of stone but he could not get the entire stone block back. This is a physical change.

1. Yes

2. No

Q. Gram molecular weight of ammonia ${\text{NH}}_3$ is:

1. 10 g
2. 45 g
3. 17 g
4. 20 g

Q. Statement 1: No New substance is formed during a physical change.

Statement 2: New substances are formed during chemical changes.

1. Both statements are true.
2. Both statements are false.
3. Only statement 1 is true.
4. Only statement 2 is true.

Q.

___________ gas is responsible for combustion.

1. Inert

2. Carbon dioxide

3. Oxygen

4. Nitrogen

Q.

(a) State the law of conservation of mass.

(b) What do you observe when barium chloride solution is mixed with sodium sulphate solution ?

Q.

Why do we need to balance a chemical reaction?

1. Mass should be conserved.

2. To balance number of radicals.

3. To make chemical equation look much better.

4. To increase the mass of products obtained.

Q.

The statement given below is incorrect. Write the correct statement.

Rusting of iron is an example of physical change.

Q. In an experiment, 15 g of a compound X is heated in a closed glass container to give compounds Y and Z. The total mass of the compounds Y and Z is ______ g.

1. 15
2. 30
3. 7.5
4. 10

Q.

Rusting of iron is a

1. physical change

2. chemical change

3. periodic change

4. fast change

Q.

Which of the following are examples of chemical reactions?

i. Burning of wood

ii. Cutting of wood

iii. Conversion of steam to water

iv. Rusting of almirah

1. i, iv

2. ii, iii

3. i, iii

4. ii, iv

Q.

Harry, John, Isha and Iqbal went for picnic. Isha was cutting some apples but in the middle of it, Harry took her to play volleyball. After coming back she saw a brown coating over the apple slices. This formation of brown coating is which kind of change?

1. Physical change

2. Chemical change

3. Both physical and chemical change.

4. Can't be said

Q. Identify the natural chemical change out of the following.

1. Lighting a matchstick
2. Folding a towel
3. Ripening of banana
4. Formation of clouds

Q.

In an experiment, 15 g of a compound X is heated in a closed glass container to give compounds Y and Z. The total mass of the compounds Y and Z is ______ g.

1. 15

2. 30

3. 7.5

4. 10

Q.

Select the correct answer from the choices A, B, C, and D which are given. Write only the letter corresponding to the correct answer.

Which is an example of a physical change.

1. Metal rusting

2. Silver tarnishing

3. Water boiling

4. Paper burning

Q.

Which of the following are the examples of a chemical reaction?

i. Burning of wood

ii. Cutting of wood

iii. Conversion of steam to water

iv. Rusting of almirah

1. i, iv

2. i, iii

3. ii, iv

4. ii, iii

Q. Fill in the blanks by choosing an appropriate option.
When sugar is dissolved in water, it undergoes a ___(i)___ change but if sugar is heated in a test tube over the Bunsen burner flame, it first melts, turns brown and finally turns ___(ii)___. The new substance formed is ___(iii)__ and the change is a ____(iv)____ change.

1. (i) - Physical reversible, (ii) - Black, (iii) - Charcoal, (iv) - Chemical irreversible
2. (i) - Physical irreversible, (ii) - Black, (iii) - Coal, (iv) - Chemical irreversible
3. (i) - Physical irreversible, (ii) - Red, (iii) - Charcoal, (iv) - Chemical reversible
4. (i) - Physical reversible, (ii) - Red, (iii) - Coal, (iv) - Chemical reversible

Q.

1. Sublimation
2. Boiling of water
3. Glowing of filament in bulb
4. Combustion

Q.

Which of the following changes indicate that a chemical change has taken place?

1. Absorption or release of heat

2. Change in colour

3. Evolution of gas

4. All of the above

Q.

Which of the following are the examples of a chemical reaction?

1. Cutting of wood
2. Conversion of steam to water
3. Rusting of iron
4. All of the above

Q.

Atomicity is the number of atoms present in a molecule.

1. False

2. True

Q. Which among the following is written on the right side of a chemical equation?

1. Heat released
2. Catalyst
3. Reactant
4. Product

Q. Classify the following into chemical and physical changes.
Combustion of LPG

Q.

When wax is burnt (in the form of a wax candle), then water and carbon dioxide are formed. This shows the "change in state" characteristic of reactions. State true or false.

1. True

2. False

Q.

In an experiment, 15 g of a compound X is heated in a closed glass container to give compounds Y and Z. The total mass of the compounds Y and Z is ______ g.

1. 15

2. 30

3. 10

4. 7.5