Answer:
There will react 30.9 milligrams of magnesium
Step-by-step explanation:
Step 1: Data given
Volume of hydrogen = 31.2 mL
Pressure = 754 torr = 754/760 = 0.992 atm
Temperature = 25.0 °C = 298 Kelvin
Step 2: The balanced equation
Mg + 2HCl → MgCl2 + H2
Step 3: Calculate moles of H2
p*V = n*R*T
⇒ with p = the pressure of H2 = 0.992 atm
⇒with V = the volume of H2 = 31.2 mL = 0.0312 L
⇒ with n = the moles of H2 = TO BE DETERMINED
⇒ with R = the gas constant = 0.08206 L*atm/K*mol
⇒ with T= the temperature = 25.0 °C = 298 Kelvin
n = (p*V)/(R*T)
n = (0.992*0.0312)/(0.08206*298)
n = 0.00127 moles
Step 4: Calculate moles of Mg
For 1 mol of Mg we need 2 moles of HCl to produce 1 mol of MgCl2 and 1 mol of H2
For 0.00127 moles of H2 we need 0.00127 moles of Mg
Step 5: Calculate mass of Mg
Mass of Mg = moles of Mg * molar mass of Mg
Mass of Mg = 0.00127 moles * 24.3 g/mol
Mass of Mg = 0.0309 grams = 30.9 mg of Mg
There will react 30.9 milligrams of magnesium