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Question
What is variable valency ? Give two examples of elements showing variable valency.
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Solution
Certain elements exhibit more than one valency, that means they show variable valency.
Ferrous is written as Iron (II) and Ferric is written as Iron (III).
| Metal | Radicals | Valency |
| Iron | Ferrous [Iron (II)] Ferric [Iron (III)] |
2 3 |
| Copper | Cuprous [Copper (I)] Cupric [Copper (II)] |
1 2 |
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Match the compounds in List I – 1 to 20 with their correct formulas in List II – A to T.
| List I | List II |
| 1. Copper [I] sulphide | A: KMnO4 |
| 2. Potassium permanganate | B: Mg3N2 |
| 3. Phosphoric acid | C: Mg(NO3)2 |
| 4. Copper [I] oxide | D: Al2(SO4)3 |
| 5. Carbonic acid | E: Na2ZnO2 |
| 6. Aluminium sulphide | F: N2O |
| 7. Iron [II] oxide | G: H2CO3 |
| 8. Iron [III] sulphide | H: Al2S3 |
| 9. Iron [II] sulphate | I: NO |
| 10. Sodium zincate | J: FeS |
| 11. Nitrous oxide | K: Fe2S3 |
| 12. Aluminium sulphate | L: H3PO4 |
| 13. Magnesium nitride | M: Cu2S |
| 14. Iron [III] sulphate | N: CuS |
| 15. Copper [II] oxide | O: Fe2O3 |
| 16. Iron [III] oxide | P: FeO |
| 17. Nitric oxide | Q: FeSO4 |
| 18. Copper [II] sulphide | R: Fe2(SO4)3 |
| 19. Iron [II] sulphide | S: CuO |
| 20. Magnesium nitrate | T: Cu2O |
