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प्रश्न
What do you observe when :
an iron nail is kept in tap water for few days
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उत्तर
We observe reddish brown coating on the nail called rust (entirely new substance) is chemical change.
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संबंधित प्रश्न
State whether the following statement is true or false. In case a statement is false, write the corrected statement.
Condensation of steam is not a chemical change.
Write the missing reactants and products and balance the equations.
NaOH + ............... `→` NaCI + ...................
FILL IN THE BLANK
In a double decomposition precipitation reaction both the reactants must be ............ soluble.
TRUE \ FALSE
Copper can displace iron from iron sulphate.
Write true or false :
Hydrogen sulphide has rotten egg smell .
Explain by writing a word equation.
Limestone powder disappears on adding to dilute hydrochloric acids.
What do you understand by precipitation reaction? Explain with examples.
State the type of reactions for the following represent and balance the ones that are not balanced.
NaOH + HCl → NaCl + H2O
Complete the following table and write your observations.
|
Hydrogen sulphide |
Ammonia |
Sulphur dioxide |
Hydrogen chloride |
|
|
Shake the gas with red litmus solution |
||||
|
Shake the gas with blue litmus solution |
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|
Apply a burning splint to a gas |
What is observed in performing the following :
| Hydrogen | Oxygen | Carbon dioxide | Chlorine | |
| Litmus test | ||||
| Apply a burning splint to the gas | ||||
| Colour of gas | colourless | colourless | colourless | greenish-yellow |
| Odour of gas |
Write your observation and a balanced equation in the case of the following substances being heated.
Ammonium chloride
Give examples of exothermic reactions i.e. heat evolved in each of the following:
(a) reaction between a solid and a liquid
(b) reaction between two gases
Give two examples of exothermic reactions seen in everyday life.
Give reason for the following:
Even though rusting is an exothermic reaction, the heat evolved when an iron nail rusts is unnoticeable.
On heating which of the following substances i.e. copper carbonate, zinc carbonate, washing soda, copper sulphate, zinc nitrate, copper nitrate, lead nitrate, ammonium chloride and ammonium dichromate – relate to the reaction given below.
A coloured substance which leaves a black residue and evolves two gases one of which is acidic and coloured and the other neutral and colourless.
Give a balanced equation for the conversion of an ammonium salt to a basic gas.
When lithium metal is placed in hydrochloric acid, _______ gas is evolved.
Which of the following is a chemical change?
Iron and rust are the same substances.
Match the following:
| Column I | Column II | ||
| 1. | Burning of coal | a. | Rusting |
| 2. | Painting of a surface | b. | Evaporation |
| 3. | Dipping iron in the water | c. | Chemical change |
| 4. | Salt from seawater | d. | Prevention of rusting |
Is the conversion of milk into ice cream a chemical change?
