How many grams of residue is obtained by heating 2.76 g of silver carbonate?

(Given : Molar mass of $\mathrm{C}, \mathrm{O}$ and Ag are 12, 16 and $108 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively)

What is the mole fraction of water in $10 \%$ by weight $(\mathrm{w} / \mathrm{w})$ of aqueous urea solution?

[Given: Molar mass of $\mathrm{H}, \mathrm{O}, \mathrm{C}$ and N are $1,16,12$ and $14 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively.]

The correct order of total number of atoms present in

(A) 2 moles of cyclohexane

(B) 684 g of sucrose

(C) 90.8 L of dihydrogen at STP

is :

Number of moles and number of molecules in 1.4187 L of $\mathrm{SO}_2$ at STP respectively are