Identify the valency of the following radicals: (a) Sulphate, (b) Hydroxide, (c) Phosphate. What is the branch of chemistry that deals with the study and manufacture of minerals? Why is it important f

7 (a)
The valency of the Sulphate radical ($\text{SO}_4^{2-}$) is $\boxed{\text{-2}}$.

7 (b)
The valency of the Hydroxide radical ($\text{OH}^{-}$) is $\boxed{\text{-1}}$.

7 (c)
The valency of the Phosphate radical ($\text{PO}_4^{3-}$) is $\boxed{\text{-3}}$.

8 (a)
The branch of chemistry that deals with the study and manufacture of such minerals (like Ammonium Nitrate fertilizer) is Industrial chemistry.

8 (b)
It is important for a chemist to use a consistent chemical formula because it ensures universal understanding and clear communication among scientists worldwide. A consistent formula uniquely identifies a substance, preventing ambiguity and allowing for accurate replication of experiments, safe handling, and reliable trade of chemical products across different regions and languages.

9 (a)
The common name given to elements in Group 18 (VIII) of the periodic table is Noble gases.

9 (b)
One practical use of these gases in the transport industry is using Helium to inflate balloons and airships. Helium is chosen because it is much lighter than air and non-flammable, making it a safe and effective lifting gas for lighter-than-air craft.