Gas Law Homework Help?

Full Question: A student used 0.1321 g of Mg and 74.35 mL of 4.000 M HCl. They collected 112 mL of hydrogen. The temperature of the room was 21.0 ˚C and atmospheric pressure was 744.6 mmHg.

How many moles of magnesium were used in this experiment?
How many moles of hydrochloric acid were used in this experiment?
Which reactant is the limiting reagent?
How many moles of hydrogen wewhat is the vapor pressure of water at this temperature? re produced?
What was the partial pressure of the gas collected in atm?
Using the data above, what is the calculated value for the gas law constant in L atm mol-1 K-1?
What is the percent error in this experimental value?

1 Answer
Jun 14, 2018

Use the basic definitions and equations to set up the calculations.


moles Mg = g Mg/(g-molecular Wt. Mg)
Moles HCl = M/L
If you mean HCl used instead of present, you first need to compare the moles of Mg with available HCl to find the limiting reagent. You need to write out the balance chemical equation to find that ratio.

Moles #H_2# = #(PV)/(RT)# in appropriate units.

mmHg/760 = atm

Plug your experimental values into the gas law equation and solve for R to compare it to the established R value.

Percent Error #= ("Actual" - "Theoretical")/"Theoretical" xx 100#