Chemical Reactions

Q.

Give two examples of the following change occurring during a chemical reaction:

Change of state of the reactants

Q.

Write the following equation and balance them.

Copper + Sulphuric acid $\to$ Copper (II) sulphate + Sulphur dioxide + Water

Q. What is a chemical equation?

Q.

Name the law which requires balancing of the chemical equations

Q. The gas used in chips packets because of its non-oxidative properties is:

1. Carbon dioxide
2. Nitrogen dioxide
3. Nitrogen
4. Hydrogen

Q.

Which among the following changes are exothermic or endothermic in nature.

Decomposition of ferrous sulphate.

Q.

How to balance metals and non metals

Q. Take some sugar in a test tube and heat it for some time. You will observe that sugar first melts, then turns brown, and finally gets charred and turns black. This experiment proves that sugar contains__________.

1. carbon
2. hydrogen
3. oxygen
4. sulphur

Q.

Complete and balance following equations $\mathrm{CuO}+{\mathrm{H}}_2\to$

Q.

A particular solution contains molecules and ions of the solute so it is a

1. Weak acid

2. Strong acid

3. Strong base

4. Salt solution

Q. N+e-=========>N- Is it endothermic or exothermic reaction

Q.

(a) Define a chemical reaction.

(b) What happens during a chemical reaction ?

(c) What do you understand by a chemical bond ?

Q.

Which of the following is not a chemical change?

1. Photosynthesis

2. Breaking a glass tumbler

3. Burning of wood

4. Rusting of iron

Q.

Fill in the blanks.

Gas carbon is a _______ conductor of electricity. (good/bad)

Q.

What causes chemical bonds to break?

Q.

Write the step-by-step method to balance a chemical reaction.

Q.

The alkali formed by the reaction of sodium with water is ____________.

1. sodium oxide

2. sodium hydride

3. sodium carbonate

4. sodium hydroxide

Q.

Charcoal is a good adsorbent.

1. True
2. False

Q.

Heating of potassium permanganate is an example of an exothermic reaction.

1. True

2. False

Q.

A student prepared an aqueous solution of barium chloride and sodium sulphate. She weighed them separately and mixed them in a beaker. A white precipitate was immediately formed. She filtered the precipitate, dried it, and weighed it again.

1. Will the weight of the precipitate be the same as that of the reactants before mixing?
2. If not so, where does the mistake?
3. Which law of chemical combination is supported by the experiment.
4. Which is the major condition that should be fulfilled to verify the law of conservation of mass.

Q.

What type of change is involved in the formation of curd from milk?

Q.

How does a skeletal chemical equation differ from a balanced chemical equation?

Q.

Write any two chemical properties of acids. [3 MARKS]

Q.

Which of the following aqueous solution will conduct an electric current quite well in comparision?

1. Glycerol

2. HCl

3. Pure water

4. Sugar

Q. Out of citric acid and dilute sulphuric acid which is stronger acid? State the reason also.

Q. Which amongst the following parameters cannot be used to identify the occurrence of a chemical reaction?

1. Change in smell
2. Change in shape
3. Absorption of heat
4. Formation of gas

Q. Magnesium ribbon on burning in air produces:​

1. magnesium oxide, water, and light​
2. magnesium oxide and heat​
3. magnesium oxide, heat, and light​
4. magnesium oxide, water, and heat​

Q.

3. Churning method is used to get:

1. Cream from milk

2. Butter from milk

3. Yogurt from milk

4. All of these

Q.

which of the following is not a chemical change?

1. Photosynthesis

2. Breaking of glass tumbler

3. burning of wood

4. rusting of iron

Q.

Name any three undesirable changes. Explain why they are considered undesirable.