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

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8