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Question
What is a chemical reaction?
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Solution
“Chemical reaction is a chemical change in which matter changes into a new substance or substances.”
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RELATED QUESTIONS
State whether the following statement is true or false. In case a statement is false, write the corrected statement.
Formation of manure from leaves is a physical change.
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A .............is a substance which changes the rate of a chemical reaction without undergoing a chemical change.
FILL IN THE BLANK
A .............. change is a temporary change.
MATCH THE COLUMNS
| 1 . `H_2` + `CI_2` `→` 2HCI | a. displacement reaction |
| 2. `2FeCI_3`+ `H_2` `→` `2FeCI_2` +2HCI` | b. addition of an electronegative redical |
| 3. Fe + `CuSO_4` `→``FeSO_4` +Cu` | c. removal of an electronegative redical |
| 4. `2H_2O` +`4NO_2`+`O_2` `→` `4HNO_3` | d.reduction by adding hydrogen |
| 5. 3Fe +`3CI_2` `→` `2FeCI_3` | e.electrolysis of water |
| 6. `FeCI_3`+ 3NaOH `→``Fe(OH)_3``↓`+NaCI | F.double decomposition,precipitation reaction |
| 7.`2H_2O` `→` `2H_2``↑`+`O_2` | e. combination or synthesis reaction |
What are chemical reactions?
Give an example of a reaction where the following are involved:
Solution
Name: A brown gas
Give a chemical test to distinguish between the following gases.
H2 and CO2
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.
Select the correct answer for the following options:
The pale blue precipitated obtained when copper [II] sulphate reacts with sodium hydroxide.
Give balanced equation for the following conversion affected by heat alone on the substance:
Ammonium dichromate to nitrogen
Give balanced equation for the following conversion affected by heat alone on the substance:
Zinc carbonate to zinc oxide
State the following reaction represent oxidation or reduction.
\[\ce{Al->Al+++}\]
Select the correct answer from the options given below:
State the gaseous product formed, when
An active metal reacts with dilute sulphuric acid.
A bag of cement lying in the open gets wet due to rain during the night. The next day the sun shines brightly. Do you think the changes, which have occurred in the cement, could be reversed?
Chemical change is a temporary change.
Two chemical species X and Y combine together to form a product P which contains both X and Y
\[\ce{X + Y -> P}\]
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition
On heating calcium carbonate gets converted into calcium oxide and carbon dioxide.
(a) Is this a physical or a chemical change?
(b) Can you prepare one acidic and one basic solution by using the products formed in the above process? If so, write the chemical equation involved.
A chemical change may involve –
______ are substances that speed up the process of a chemical change and it will not undergo any change during the course of the reaction.
