Question

4) How many grams of F2, gas occupy 4.9 L at STP?

Answer 1

We know two equations that can help as answer:

n = m/Mr

• "n" --> number of moles
• "m" --> mass (kg)
• "Mr" --> molecular mass of the substance

n = V/Vm

• "V" --> volume of gas
• "Vm" --> a constant which value is 22.4 for STP conditions

So, combining the two equations above:

m/Mr = V/Vm

m = V×Mr/Vm

• V = 4.9L
• Mr = 38 *
• Vm = 22.4

m = 8.31 gr

*To calculate the Mr of "F2" we need to multiply by 2 the atomic mass of F, which we can find onlu by looking it up in a table (probaly in the back of a chemistry book, or online). We see that it is equal to 19, so Mr will be equal to 38.

**The equations are derived easily. Lets take for example the first one. 1 mole of the substance contains Mr gr of it. So, how many gr do "n" moles contain?

Answer 2

8.31g

Step-by-step explanation:

First, we calculate the molar mass of F2.

MM of F2 = 2 x 19 = 38g/mol

But,

1mol of a gas occupy 22.4L at stp.

This implies that 1mole(i.e 38g) of F2 occupies 22.4L.

Therefore, Xg of F2 will occupy 4.9L i.e

Xg of F2 = (38 x 4.9) / 22.4

Xg of F2 = 8.31g

Therefore 8.31g of F2 occupies 4.9L