Question

Given,$0.75g$ Platinic chloride, a monoacidic base on ignition gives$0.245g$platinum. The molecular weight of the base is
A.$75g$
B.$93.5g$
C.$100g$
D.$80g$

Answer 1

We need to know that the platinic chloride is also known as chloroplatinic acid is a inorganic having the chemical formula, ${\left[ {{H_3}O} \right]_2}{\left[ {PtC{l_6}} \right]_X}$. It is a solid compound which is red in colour. And it is a major commercial source of platinum. Generally, it is found as an aqueous solution. Platinic chloride is the hydronium salt of hexachloroplatinate.

Complete answer:
The molecular weight of the base is not equal to $75g$. Hence, option (A) is incorrect.
Given, the weight of platinic chloride is equal to$0.75g$. And when it is ignited there is a formation of $0.245g$ platinum.
Weight of ${B_2}{H_6}PtC{l_6}$ is equal to the weight of platinum.
Consider the equation,
$\dfrac{{wt.of\,{B_2}{H_2}PtC{l_6}}}{{2B + 410}} = \dfrac{{Wt.of\,Pt}}{{mol.wt\,of\,Pt}}$
Where, the molecular weight of platinum is equal to $195$. Thus substitute the values in above equation, will get
$\dfrac{{0.75}}{{2B + 410}} = \dfrac{{0.245}}{{195}}$
By simplifying the equation, will get the value of B and that is, $B = 93.5$
Equivalent weight of base is equal to $93.5$, since it is monobasic.
Therefore, the molecular weight of base $= 93.5 \times 1 = 93.5$
Hence, option (B) is correct.
By using the given values, the molecular weight of base is not equal to $100g$. Hence, option (C) is incorrect.
The molecular weight of the base is not equal to $80g$. Hence, the option (D) is incorrect.

Hence, option (B) is correct.

Note:
According to the monoacidic base, the base will produce the hydroxide ion by the ionization reaction of the molecule. And the example is sodium hydroxide and potassium hydroxide. And in the case of a diacidic base is a base and it produces more than two hydroxide ions by complete ionization reaction.