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प्रश्न
State what you would observe when the following substance is heated in a glass test tube red lead.
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उत्तर
2Pb3O4 → 6PbO + O2 ↑
The dark red lead as red powder changes to yellow colour. The yellow colour residue on further heating sticks to the tube and give reddish colour to glass. A colourless and odourless gas is evolved.
APPEARS IN
संबंधित प्रश्न
Complete and balance the following chemical equations
NaCI + `AgNO_3` `→`
Fill in the blanK
A .............is a substance which changes the rate of a chemical reaction without undergoing a chemical change.
Write the missing reactants and products and balance the equations.
\[\ce{KClO3 ->[heat]}\] ___________+ ____________
FILL IN THE BLANK
On reaction with sulphuric acid solution, barium chloride forms a white precipitate of ........ sulphate.
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 |
TRUE \ FALSE
The evolution of a gas during a chemical reaction is shown by an arrow pointing downwards. True or false ?
Fill in the blank:
In some chemical reactions an insoluble ________ is formed when two solutions are mixed.
Write true or false :
When iron and sulphur are heated together a grey mass is formed which is attracted by a magnet .
Give an example of a reaction where the following are involved
Light
When hydrogen burns in oxygen, water is formed; when electricity is passed through water, hydrogen and oxygen are given out. Name the type of chemical change involved in the two cases.
Give an example of the following chemical changes.
A reaction where colour change is noticed.
State the main characteristics of chemical reactions. Give at least one example in each case.
State the original colour of the following substance and colour of residue obtained after heating.
Copper carbonate
Complete the table given below.
| Addition of dil. H2SO4 to FeS | Odour of gas evolved |
Mention the various conditions required for a chemical reaction to occur.
Give two examples for the following case:
Chemical changes
Heat may evolve or be absorbed during a ______ change.
The chemical name of baking soda is sodium bicarbonate.
Both CO2 and H2 gases are ______.
______ is the chemical name of slaked lime.
