What is the mass concentration of #"0.05 N"# #"HCl"#?

1 Answer
Truong-Son N.
Aug 18, 2016

Normally (pun intended?), normality would tell you the equivalent concentration of protons for a given acid. So if you had #"1 M"# #"H"_2"SO"_4#, it would actually be #"2 N"# #"H"_2"SO"_4#, since there are two protons per molecule of #"H"_2"SO"_4#.

However, since #"HCl"# is monoprotic, #"0.05 N HCl"# #=# #"0.05 M HCl"#.

Therefore, you should have #"0.05 mols HCl"/"L soln"#, or:

#"0.05" cancel"mols HCl" xx "36.4609 g HCl"/cancel"1 mol HCl"#

#= color(blue)("1.82 g HCl"/"L soln")#

Even though #0.05# has only one sig fig, realistically you could easily measure at least to the hundredths place for the mass, so you can have more like #"0.0500 M HCl"#.

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