Question

q7. the number of moles of sulfur trioxide molecules in 155 grams is: a) 80.1 moles. b) 1.94 moles. c) 0.517 moles. d) 3.45 moles.

Explanation:

Step1: Calculate molar mass of $SO_3$

The molar mass of S is 32.07 g/mol and O is 16.00 g/mol. For $SO_3$, molar mass $M=(32.07 + 3\times16.00)$ g/mol = 80.07 g/mol.

Step2: Use mole - mass formula

The formula to calculate the number of moles $n$ is $n=\frac{m}{M}$, where $m = 155$ g and $M = 80.07$ g/mol. So $n=\frac{155}{80.07}\approx1.94$ moles.

Answer:

B. 1.94 moles