Chemical Reactions

Q.

Write a chemical equation for the reaction of:

(3) Potassium with water

Q. On heating, calcium carbonate get converted in calcium oxide and carbon dioxide.
a.) Is this a physical or chemical change
b.) Can you prepare one acidic and one basic solution by using the products formed in the above process, write the chemical equation involved?

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Q.

Classify the following into element, compound, and mixture:

dry ice

Q.

Write the word equation for the reaction:

Magnesium burns in carbon dioxide to form magnesium oxide and carbon.

Q.

Cl2 stands for:

1. 2 molecules of chlorine

2. 2 atoms of chlorine

3. 2 ions of chlorine

4. 3 molecule of chlorine

Q.

Which of the following metals is not amphoteric in nature?

1. Aluminium

2. Copper

3. Lead

4. Zinc

Q.

Question 35
Iron fillings and sulphur were mixed together and divided into two parts, 'A' and 'B'. Part 'A' was heated strongly while part 'B' was not heated. Dilute hydrochloric acid was added to both the parts and evolution of gas were seen in both the cases. How will you identify the gases evolved?

Q.

Classify the following changes as chemical and physical change:

Rusting of almirah

Q.

The products are always written on the right-hand side in a chemical equation with a plus sign (+) between them.

1. True
2. False

Q.

An element X reacts with dilute H₂SO₄ as well as with NaOH to produce salt and H₂(g). Hence, it may be concluded that:

A. X is an electropositive element.
B. Oxide of X is basic in nature
C. Oxide of X is acidic in nature.
D. X is an electronegative element.

1. A , B, C

2. D, A, B

3. C, D, A

4. B, C, D

Q. The explosion of fireworks is an example of __________ change.

1. physical
2. chemical
3. temporary
4. natural

Q.

On heating hydrated copper sulphate, it turns _________ colour.

1. Yellow

2. Blue

3. White

4. Green

Q.

Which of the following statements is correct about a chemical change?

1. The chemical change is always accompanied with the liberation or absorption of energy

2. The change is temporary and reversible

3. There is no change in weight of substance

4. No new products are formed

Q.

What is the Greek name of Mercury and write its symbol?

Q.

Does the physical state of a substance always change during a chemical change? Give one example in favour and one example against the statement with proper reasoning.

Q.

In the Haber process, Nitrogen and Hydrogen react to form Ammonia.

Which factor increases both the speed of reaction and the amount of Ammonia produced?

1. Addition of a catalyst

2. Decreasing the temperature

3. Increasing the pressure

4. Increasing the temperature

Q.

What is/are the catalyst used for the formation of Ammonia.

1. Iron

2. Molybdenum

3. Zinc

4. Magnesium

Q. A scientist while working on an experiment found a compound with chemical formula $Fe(HC{O}_3{)}_3$. What is its atomicity?

1. 6
2. 16
3. 15
4. 8

Q. The volume of hydrogen gas evolved during electrolytic decomposition of water is ________ time the amount of oxygen gas evolved.

1. three
2. two
3. eight
4. four

Q.

What is meant by a chemical equation? Write the steps involved in writing the chemical equations.

Q.

Write the symbol for Bromine.

Q.

Which of the following statement is correct?

1. Both burning of a paper and cooking of food are examples of a physical change

2. Both burning of wood and cooking of food are are examples of a chemical change

3. Burning of a paper is a physical change and cooking of food is a chemical change

4. Burning of a paper is chemical change and cooking of food is a physical change

Q.

Why are the chemical properties of isotopes same?

Q.

The chemical symbol for nitrogen gas is

Q.

4. A potato remains a potato even after it is cooked so it should be physical change. Do you agree? Give example.

Q.

Classify the following into physical and chemical change.
Rusting of iron

Q.

What happens when boiling water is added to a mixture of Iron ($\mathrm{Fe}$) filings and Sulphur ($\mathrm{S}$) powder?

1. Both $\mathrm{Fe}$ and $\mathrm{S}$dissolve to form a clear solution.

2. $\mathrm{Fe}$ precipitates, but $\mathrm{S}$ dissolves to form a pale yellow solution.

3. A black precipitate of $\mathrm{FeS}$ is obtained.

4. A black suspension containing undissolved $\mathrm{Fe}$ filings and $\mathrm{S}$powder is obtained.

Q. If 56 g of calcium oxide reacts with a certain amount of water (X g), a new compound with mass 74 g is formed. The value of X (in g) is

1. 
   130
2. 
   92
3. 
   18
4. 
   8

Q. Which of the following is not an example of a chemical reaction?

1. Melting ice
2. Burning wood
3. Rusting of an iron rod
4. Photosynthesis in plants

Q.

State whether the following is possible.

Using copper and hydrochloric acid to produce hydrogen gas.