# When using the formula PV = nRT, why is R = 82.05746? An example of when using this formula is below, which is a question I have previously asked already.What is the amount of hydrogen released in...

When using the formula PV = nRT, why is R = 82.05746? An example of when using this formula is below, which is a question I have previously asked already.

What is the amount of hydrogen released in the following case:

Silicon steel is an alloy of the elements iron, carbon and silicon. An alloy sample was reacted with excess hydrochloric acid and the following reaction occurred:

Fe (s) + 2HCl (aq) ---> FeCl2 (aq) + H2 (g)

The carbon and silicon in the alloy did not react with the acid. If an alloy sample with a mass of 0.160 g produced 62.0 mL of hydrogen gas, measured at SLC, calculate the amount of hydrogen evolved in the reaction.

When finding the answer by using the formula of PV = nRT, why is R = 82.05746? I thought it was just 8.31, please explain to me why this is so..

The answer to this question was:

When a sample of silicon steel that is made up of iron, carbon and silicon is reacted with excess hydrochloric acid the following reaction occurs:

Fe (s) + 2HCl (aq) ---> FeCl2 (aq) + H2 (g)

The mass of the sample used is 0.16 g and the volume of hydrogen produced when measured at standard laboratory conditions with a temperature of 25 C and a pressure of 1 atm. is 62 mL

The amount of hydrogen released can be calculated using the ideal gas law, PV = n*RT, where P is the pressure, V is the volume, n is the amount of the gas in moles, T is the temperature and R is a constant.

1*62 = n*82.05746*298