What is the molar mass of manganese(II) nitrate tetrahydrate Mn(NO3)2·4H2O)?

Manganese Nitrate Tetrahydrate

Method 1 : by calculation

Relative atomic mass :
Mn = 54.94, N = 14.01, O = 16.00, H = 1.01

Molar mass of Mn(NO₃)₂•4H₂O
= 54.94 + 14.01×2 + 16.00×10 + 1.01×8
= 251.04 g/mol


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Method 2 : by searching in web

For example, according to the following web-page :
http://www.endmemo.com/chem/compound/mnno3_24h2o.php

Molar mass of Mn(NO₃)₂•4H₂O = 251.009 (g/mol)

You simply add up the molar masses of all of the atoms in the compound.

Mn + 2 N + 6 O + 8 H + 4 O
54.94 + 2(14.01) + 6(16.00) + 8(1.01) + 4(16.00) = 251.04 g/mol