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प्रश्न
Explain with the help of balanced equations, how precipitation reactions are used for identifying the positive radicals in three different salts, each having a different cation [positive ion].
उत्तर
Precipitation reactions are used to identify the positive ions from their colours.
\[\ce{CuSO4 + 2NaOH->Na2SO4 + \underset{\text{pale blue ppt.}}{Cu[OH]2 v}}\]
identified ion is \[\ce{Cu^2+}\]
\[\ce{FeCl3 + 3NaOH->3NaCl + \underset{\text{reddish brown ppt.}}{Fe[OH]3 v}}\]
identified ion is \[\ce{Fe^3+}\]
\[\ce{Pb[NO3] + 2NaOH->2NaNO3 + \underset{\text{chalky white ppt.}}{Pb[OH]2 v}}\]
identified ion is \[\ce{Pb^2+}\]
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संबंधित प्रश्न
How would you show that setting of curd is a chemical change?
FILL IN THE BLANK
In a ............ change, new substances are formed.
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 the characteristics of a chemical reaction ? A chemical reaction is characterised by an irreversible change in which a new substance is formed.
Write true or false.
A chemical equation gives only qualitative information of a chemical reaction.
Balancing a chemical equation is based on
Show with the help of diagram of electronic configuration how the following compound is formed from the constituent atoms.
Water
Give an example of a reaction where the following are involved
Heat
Give an example of the following chemical changes.
A reaction involving
(i) Change of state
(ii) formation of precipitate
State the original colour of the following substance and colour of residue obtained after heating.
Zinc carbonate
State the following reaction represent oxidation or reduction.
\[\ce{H->H+}\]
Give a suitable example with an equation to show the representation of a chemical reaction.
What happens when cane sugar is strongly heated? Mention any two changes in it.
Photosynthesis is a chemical reaction that takes place in the presence of ______.
Arrange the following statements in correct sequence:
- One side is water-loving and other water-hating molecules.
- When you agitate the cloth, the dirt is surrounded by many molecules and taken away from the cloth.
- The dirt surrounded by the detergent molecules floats in the water making it dirty.
- Finally, the cloth is clean.
- The detergent molecules have two sides.
- Water hating goes and joins with dirt and oil in the cloth while the water-loving joins with the water molecules.
Classify each of the following, as a physical or a chemical change. Give reasons.
(a) Drying of a shirt in the sun.
(b) Rising of hot air over a radiator.
(c) Burning of kerosene in a lantern.
(d) Change the colour of black tea by adding lemon juice to it.
(e) Churning of milk cream to get butter.
Give an example of a chemical reaction for each of the following situations:
A change in colour is observed.
The chemical name of baking soda is sodium bicarbonate.
Assertion (A): Cutting paper into very small pieces is an irreversible change.
Reason (R): Physical changes are always reversible.
What is the difference between reactants and products?
