Don’t know how to solve this

Question

1) A tank of Bromine gas occupies 15 L at a pressure of 160 kPa at 25 deg C. How many grams of Bromine are in the tank?

Answer 1

The first thing I asked myself was, "what is needed to find out how many grams of a substance I have?" Often in chemistry, you have to first figure out how many moles of that substance you have.

This lead me to my next question, "how can I figure out the number of moles of a gas?"

Luckily, I remembered my ideal gas equation.... PV=nRT

P = the pressure in kPa = 160

V= volume in liters = 15

n = number of moles = unknown

R = the ideal gas constant = 8.314

T = temperature in Kelvin = 298

I added 273 to the temperature to convert it into Kelvin

25+273 = 298

T = 298 K

Plugging everything into the equation we get

(160)(15) = n(8.314)(298)

Rearrange and solve for n

n = 0.96869 moles

Finally, we can convert moles of Bromine (gas) into grams.

Since Br gas is diatomic (2 atoms of bromine per 1 molecule of gas), you multiply the number of moles by 2.

Then you convert moles of Br atoms into grams by multiplying it by the molar mass (79.94 g/mol Br).

The full equation is as follows

(0.96869 moles Br gas)*(2 moles Br/ 1 mole Br gas)*(79.94 grams/mol) = 154.87 grams Bromine gas

Final answer: 154.87 grams of Br gas

Answer 2

Bromine (gas) is diatomic, Assume it is an ideal gas, user the Universal Gas Equation.