We know, Given mass = Molar mass * Number of moles.
A.) <span>1.25 mol CaF</span>₂
Number of moles = 1.25
Molar mass = 78
So, Mass = 78 * 1.25 = 97.5 g
B.) 3.4 mol (NH₄)₂SO₄
Number of moles = 3.4
Molar mass = 132
Mass = 3.4 * 132 = 448.8 g
Hope this helps!
Answer : The rate of effusion of sulfur dioxide gas is 52 mL/s.
Solution :
According to the Graham's law, the rate of effusion of gas is inversely proportional to the square root of the molar mass of gas.

or,
..........(1)
where,
= rate of effusion of nitrogen gas = 
= rate of effusion of sulfur dioxide gas = ?
= molar mass of nitrogen gas = 28 g/mole
= molar mass of sulfur dioxide gas = 64 g/mole
Now put all the given values in the above formula 1, we get:


Therefore, the rate of effusion of sulfur dioxide gas is 52 mL/s.
Answer: c
Explanation: all the other answers are physical changes
"Saltation" which is the movement of hard particles such as sand over an uneven surface in a turbulent flow of air or water.
Answer: The molecular formula will be 
Explanation:
Molecular formula is the chemical formula which depicts the actual number of atoms of each element present in the compound.
Empirical formula is the simplest chemical formula which depicts the whole number of atoms of each element present in the compound.
To calculate the molecular formula, we need to find the valency which is multiplied by each element to get the molecular formula.
The equation used to calculate the valency is:

empirical mass of 
Molecular mass= 214 g/mol

Thus molecular formula will be 