For many (but not all) problems, you can simply round the atomic weights and the molar mass to the nearest 0.1 g/mole. HOWEVER, make sure that you use at least as many significant figures in your molar mass as the measurement with the fewest significant figures. In other words, never let your molar mass be the measured value that determines how many signficant figures to use in your answer!
1 mol --- 22,4 dm³
2,1 mol --- X
X = 2,1×22,4
X = 47,04 dm³ = 47,04 L
C)
119.37 g/mol
<h3>Further explanation</h3>
Relative atomic mass (Ar) and relative molecular mass / molar mass (M)
the molar mass/molecular mass of a compound : the sum of the relative atomic mass (Ar) of the constituent atoms
M AxBy = (x.Ar A + y. Ar B)
Atomic weight (Ar) of :
- C : 12.0107 g/mol
- H : 1.00784 g/mol
- Cl : 35.453 g/mol
The molar mass of CHCl₃

Answer:
Ca is larger than the Ca2+ because Ca2+ has a greater positive charge and electrons repel the nucleus.