HOW TO USE CALCULATOR

3.3. Molecular weight calculations

Calculator for Chemists translates the chemical formula into mathematical text, and replaces the element symbols with their atomic weight. The appearance of mathematical expression, which is the result of the translation, can be seen if the mouse pointer is held over the tasks field.

The element symbols can be written in lowercase letters, and the intelligent routine in the program will try to translate them and will show the result of translation - or it will report an error.

• for indicating hydration use + sign CuSO4+5H2O
• leading number is correctly typed before formula: 3CO2
• it is also possible to use all types of parentheses to define the chemical formula 12.6/{K3[Fe(CN)6]}

The relative molecular weight of the substance will be defined as the sum of relative atomic weights of the elements, multiplied by the number of atoms in the formula of this substance.

Any atom in periodic system can be used in the chemical formula. The symbol of the atom is a capital letter if it consists of only one character, such as S for sulfur or N for nitrogen. If the symbol consists of two characters then only the first one is a capital letter, such as Si for silicon or Na for sodium.

For example, when manual calculating the relative molecular weight of lead-nitrate, you must type the correct chemical formula

Pb(NO3)2

Make a list of each element and the number of atoms of each element present in the substance:

Pb*1
N*1*2
O*3*2

Go to periodic table and determine the relative atomic weights of each element, and multiply by the number of atoms in the formula:

Pb207.2*1 = 207.2
N14.00674*2 = 28.01348
O15.9994*6 = 95.9964

Sum of weights of the each elements give relative molecular weight of the lead-nitrate.

Pb(NO3)2 = 207.2 + 28.01348 + 95.9964 = 331.2098

When calculating the relative molecular weight of a copper(II) sulfate pentahydrate, type

cuso4+5h2o

And the smart converter will translate this text in the correct chemical formula

CuSO4+5H2O

If the chemical formula contains a mathematical operator (such as +, *, /, ...), smart converter will automatic add the parentheses in the expression

(CuSO4)+5*(H2O)

The next step is the convert of chemical formula into the mathematical expression

(Cu+S+O*4)+5*(H*2+O)

and the change of chemical symbols with the molecular weight for each element

(63.546+32.066+15.9994*4)+5*(1.00794*2+15.9994)

The last step is calculate this created mathematical expression and display task and results

h2so4 = H2SO4 = 98.07848
caco3 = CaCO3 = 100.0869
cocl2 = COCl2 = 98.9161
Cocl2 = CoCl2 = 129.839195
cu(nh4)2 = Cu(NH4)2 = 99.62292
ch3cooh = CH3COOH = 60.05196
h2ptcl6 + 6h20 = H2PtCl6+6H20 = 530.77068