All faculty members are happy to see students each other. dumbledore is particularly with hermione. though, it should be mentioned that students should not simply copy off each other. you will not learn anything that way. snape glares at ron slouches in his chair. snape thinks it’s time for a harder problem. how many milligrams of magnesium reacts with excess hcl to produce 31.2 ml of hydrogen gas at 754 torr and 25.0◦c. the hydrogen is produced by the following reaction:
30.7 mg of Magnesium
Explanation: The equation of reaction is;
Mg(s) + 2HCl(aq) > MgCl2(aq) + H2(g).
I mol of Magnessium produces 1 mol of Hydrogen gas.
Pressure,p= 754 torr, volume, v= 31.2 ml( which is also equals to 0.0312L) , R= 62.36367L torr/kmol, temperature, T = 25 + 273.15)
Step 1: find the number of moles using PV = nRT.
Making n(number of mole) the subject of the formula, we have;
n = PV/RT
Substitute the above parameters into the formula, we have;
n= (754 Torr) x (0.0312 L) / ((62.36367 L torr/K mol) x (25.0 + 273.15) K) = 0.001265 mol of Hydrogen gas.
Step 2: using n = mass/molar mass.
Mass = n × molar mass
(0.001265 mol of H2) x (1 mol Mg / 1 mol H2) x (24.30506 g Mg/mol) = 0.030745 g = 30.7 mg of Magnessium
Based on the given chemical reaction, as 31.2 mL of hydrogen are yielded, one computes its moles via the ideal gas equation under the stated conditions as shown below:
Now, since the relationship between hydrogen and magnesium is 1 to 1, one computes its milligrams by following the shown below proportional factor development:
Answer : The mass of required is 30.38 mg.
To calculate the moles of hydrogen gas, we use the equation given by ideal gas :
PV = nRT
P = Pressure of hydrogen gas = 754 torr
V = Volume of the hydrogen gas = 31.2 mL = 0.0312 L
n = number of moles of hydrogen gas = ?
R = Gas constant =
T = Temperature of hydrogen gas =
Putting values in above equation, we get:
Now we have to calculate the moles of .
The balanced chemical reaction is:
From the balanced chemical reaction, we conclude that
As, 1 mole of produced from 1 mole
As, mole of produced from mole
Now we have to calculate the mass of .
Molar mass of = 24 g/mol
conversion used : (1 g = 1000 mg)
Therefore, the mass of required is 30.38 mg
i just learnt this recently but i need to look through my notes again