Question

How many liters of gaseous hydrogen bromide at 82°C and 0.670 atm will a chemist need if she wishes to prepare 3.50 L of 1.20 M hydrobromic acid?

_____L HBr

Answer 1

We can apply the ideal gas law, PV = nRT

First, we need to calculate the amount and mol of HBr is required.

3.50 L of 1.20 M HBr solution to be prepared.

1 mol in 1 L = 1M

Or 1M 1L = 1 mol

Now, 1.20 M, 1L = 1.2 mol

So, 1.20 M , 3.5 L = 1.2*3.5 mol = 4.2 mol. This is the mol ‘n’ in the gas law.

Now, in the gas law only unknown is the V.

V = nRT/P, replacing the values,

We get, V = 4.2 mol * 0.082 L-atm K^-1 mol^-1 *(273+82) K/0.670 atm =182.48 Liter of HBr gas is required for preparing the given solution.