Question

2.76 gram of silver carbonate on being strongly heated yields a residue weighing:

(Ag=108, C=12, O=16)

A) 2.16g

B) 2.32g

C) 2.48g

D) 2.64g

Answer 1

In this question we should start the solution by first calculating the molecular weight. And then we should remember that, when we heat silver carbonate, there will be emission of carbon dioxide. And from this we can calculate the residue.

Complete answer:

We should know that silver carbonate is the chemical compound with the formula Ag $_2$ CO $_3$ . Silver carbonate is yellow but typical samples are grayish due to the presence of elemental silver. It is poorly soluble in water, like most transition metal carbonates.

We should know about the thermal decomposition of silver carbonate. Unlike other metal carbonates that usually decompose into metal oxides liberating carbon dioxide, silver carbonate on heating decomposes into elemental silver liberating mixture of carbon dioxide and oxygen gas.

$A{{g}_{2}}C{{O}_{3}}(s)\xrightarrow{heat}2Ag(s)+C{{O}_{2}}(g)+\dfrac{1}{2}{{O}_{2}}(g)$

Molecular Weight of $A{{g}_{2}}C{{O}_{3}}$ ​=276 g

And, molecular weight of Ag =2×108=216 g

276 g of $A{{g}_{2}}C{{O}_{3}}$ gives 216 g Ag.

So, by unitary method we will calculate this.

If 276 gram of $A{{g}_{2}}C{{O}_{3}}$ gives 216 gram of Ag.

Then, to calculate amount of silver given by 2.76 gram of $A{{g}_{2}}C{{O}_{3}}$ we must calculate amount of silver given by one gram of $A{{g}_{2}}C{{O}_{3}}$ .

So, amount of silver given by one gram of $A{{g}_{2}}C{{O}_{3}}$ will be $=\dfrac{216}{276}$

Now, to calculate amount of silver produced by 2.76 gram silver carbonate, we have to do the product of silver produced by one gram $A{{g}_{2}}C{{O}_{3}}$ and 2.76 gram silver carbonate.

So, amount of silver produced from 2.76 g $A{{g}_{2}}C{{O}_{3}}$ will be: $=\dfrac{216}{276}$ $\times 2.76$ = 2.16 gram

So, from the above discussions and calculation we find out the amount of silver produced by 2.76 gram that is 2.16 gram of silver.

So, our correct answer is option A.

Note: We should note that the principal use of silver carbonate is for the production of silver powder for use in microelectronics. It is reduced with formaldehyde, producing silver free of alkali metals. Silver carbonate is used as a reagent in organic synthesis such as the Koenigs-Knorr reaction.