Which of the following sample weighs least ?A     112 litres of ethane at STPB     1 gram atom of silverC     5 moles of nitrogenD     124 grams of phosphorous

To answer this question, we need to convert all the given quantities into grams.

A. 112 litres of ethane at STP At STP, 1 mole of any gas occupies 22.4 litres. The molar mass of ethane (C2H6) is approximately 30 g/mole. Therefore, 112 litres of ethane is equivalent to (112/22.4) moles = 5 moles. So, the weight of 112 litres of ethane at STP is 5 moles * 30 g/mole = 150 grams.

B. 1 gram atom of silver 1 gram atom of any element is equal to its atomic weight in grams. The atomic weight of silver (Ag) is approximately 107.87 g/mole. Therefore, 1 gram atom of silver weighs 107.87 grams.

C. 5 moles of nitrogen The molar mass of nitrogen (N2) is approximately 28 g/mole. Therefore, 5 moles of nitrogen weigh 5 moles * 28 g/mole = 140 grams.

D. 124 grams of phosphorous This is already given in grams.

Comparing all the weights, we find that 1 gram atom of silver (107.87 grams) weighs the least. So, the answer is B. 1 gram atom of silver.