The metal oxides obtained from roasting are then reduced to corresponding metals by using reducing agents like carbon or using displacement reactions with which of the following metals?
A. Sodium
B. Calcium
C. Mercury
Important Questions on Matter and its States
Consider the following statements:
. Rust is formed by the reaction of iron and oxygen in the presence of water or air moisture.
. In saltwater, iron tends to rust more quickly.
Which of the statements given above is/are correct?
When iron is left exposed to open air, it gets rusted. Which constituent(s) of the atmosphere is /are responsible for rusting iron?
(i) Oxygen gas present in the air.
(ii) Moisture present in the air.
(iii) Carbon dioxide gas is present in the air.
Select the correct answer using the code given below:
Identify the correct statements.
1. The freezing of water into ice is a chemical change.
2. The changes occur inside the molecular composition is a chemical change.
3. A new substance is obtained in a chemical change.
4. The change in shape, size and state is a chemical change.
Select the correct answer from the given below code.
Consider the following statements:
1. Albo iron does not rust in a vacuum because air is necessary for rusting.
2. Rust is faster in sea water because of dissolved salts.
Which of the statements given above is/are correct?
Read the following examples from daily life and select the appropriate option.
1. When food gets spoiled, then it produces a foul smell.
2. A slice of apple acquires brown colour when kept out for some time.
3. When an ant bites, then calamine is used to ease the irritation on the skin.
Which of the following ways can be used to prevent the rusting of iron?
1. Galvanization
2. Alloying
3. Reaction with acid
4. By applying paint
Select the correct answer using the codes given below:
Consider the following statements:
1. Silver articles become black after sometimes when exposed to air because they react with sulphur in the air to form a coating of silver sulphide.
2. Copper reacts with moist carbon dioxide in the air and lose its shiny brown surface and gains a green coat of copper carbonate.
3. Iron when exposed to moist air for a long time, acquires a coating of a brown flaky substance called rust.
Which of the statements given above is/are correct?
When a candle burns _____.
1. its size decreases
2. there is melting of the wax
3. flame and soot can be seen
4. melted wax also solids
From the above observations, which one of the following is correct?
