Question
Tue November 22, 2011 By:

# can you please give me the formulae on finding the number of moles and mass?

Wed November 23, 2011
Number of moles can be calculated using the following formula:
1. 1 mole of a pure substance has a mass in grams equal to its molecular mass (MM) [also known as molecular weight (MW) or formula mass (FM) or formula weight (FW)].
This is often referred to as the molar mass.

Carbon weighs 12.01 g/mole

Hydrogen weighs 1.008 g/mole
Oxygen weighs 16.00 g/mole

2. number of moles = weight in grams/ mass

TO find molar mass:

1 mole of a pure substance has a mass in grams equal to its molecular mass (MM).
eg, 1 mole of Helium (a monatomic gas with the formula He) has a mass equal to its relative atomic mass, 4.003g
eg, 1 mole of hydrogen gas (a diatomic gas with the formula H2) has a mass equal to 2 x 1.008 = 2.016g
eg, 1 mole of ammonia gas (NH3) has a mass equal to 14.01 + (3 x 1.008) = 17.034g
eg, 1 mole of water (H2O) has a mass equal to (2 x 1.008) + 16.00 = 18.016g

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