Question

I. Magnesium hydroxide is a strong base.
II. Hydroxides of alkali metals and most alkaline earth metals are strong bases.
(A) Statement I is true, statement II is true.
(B) Statement I is true, statement II is false.
(C) Statement I is false, statement II is true.
(D) Statement I is false, statement II is false.

Answer 1

Hint: The answer to this question is mainly based on the concept of solubility where in general, more basic the compound is more will be the solubility but in case of alkali and alkaline earth metals, strength of hydroxides increases and the answer lies in this fact.

Complete Solution:
We have studied about the basic concepts in the chemistry chapters that deal with solubility and also how to measure the strength and basicity of the compounds.
We shall now see the variation accordingly about the given statement in question and shall deduce the required answer.
- Alkalis are the basic, ionic salt of an alkali metal and can also be said as bases which dissolve in water.
- Bases are the compounds which are able to accept protons or compounds which are able to donate electrons.
- Here, Magnesium hydroxide is an alkali but a very weak alkali and doesn’t solubilise completely in water although the dissolved portion is considered a strong base due to complete dissociation of its ions..
- It dissociates completely but doesn’t get completely dissolved in water and therefore, it is considered as a weak alkali.
- Alkali metals such as sodium, potassium, etc. and alkaline earth metals like calcium, magnesium, etc. are strong bases due to their ability to donate electrons to hydroxyl groups and readily get ionized.
- Therefore, magnesium hydroxide is a strong base and hydroxides of most alkali metals and alkaline earth metals are strong bases.

So, the correct answer is “Option A”.

Note: Note that magnesium hydroxide is produced in large quantities from seawater by the addition of calcium hydroxide also called as milk of lime and is the primary raw material used in the production of magnesium metal and also as fire-retardant additive. This point may help you to know about natural preparation done for magnesium hydroxide.