How to find grams in moles?

The calculator below calculates the mass of the substance in grams or the quantity of the substance in moles. Depending on the input data it can serve either as grams to moles calculator or as moles to grams calculator. It also displays the molar mass of the chemical substance and details of its calculation just for reference. You can find more information and formulas about grams to moles conversion as well as about moles to grams conversion below the calculator.

Note: Always use the upper case for the first character in the element name and the lower case for the second character as in the periodic table. Compare: Co - cobalt and CO - carbon monoxide. Thus, Na3PO4 — correct notation, na3po4/NA3PO4 — incorrect notation.

There is a simple relation between grams and moles: , where - mass of the substance in grams - quantity of the substance in moles - molar mass of the substance in grams/mole

You need to divide the mass of the substance by the molar mass of the substance:

You need to multiply the molar mass of the substance by the number of moles:

As you can see, the most difficult task here is finding out the molar mass of the substance.

The molar mass is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by the amount of substance. The molar mass of atoms of an element is given by the standard relative atomic mass of the element multiplied by the molar mass constant, 1 × 10−3 kg/mol = 1 g/mol. The molar mass of a compound is given by the sum of the standard atomic weight (namely, the standard relative atomic mass) of the atoms which form the compound multiplied by the molar mass constant. Multiplying by the molar mass constant ensures that the calculation is dimensionally correct: standard relative atomic masses are dimensionless quantities (i.e., pure numbers), whereas molar masses have units (in this case, grams/mole).

And this is where our grams to moles/moles to grams calculator shines, thanks to our other calculator - Molar mass of the substance, which calculates molar mass for a substance given the formula.

All you need to do is correctly enter your formula, choose whether you want a conversion from grams to moles or a conversion from moles to grams, and, in case of g to mol, enter the mass, or, in case of mol to g, enter the moles.

Problem: Convert 25.0 grams of KMnO4 to moles. Solution:

And here is how you should enter this problem into the calculator above: grams to moles problem solution

To correctly estimate the number of moles, n , of a substance of a specific mass, m , (in grams), you need to follow the grams to moles formula: n = m / M , where: M is the molar mass of this material.

Problem

Determine the number of moles of CO2 in 454 grams of CO2.

Solution

First, look up the atomic masses for carbon and oxygen from the periodic table. The atomic mass of C is 12.01, and the atomic mass of O is 16.00. The formula mass of CO2 is:

12.01 + 2(16.00) = 44.01

Thus, one mole of CO2 weighs 44.01 grams. This relation provides a conversion factor to go from grams to moles. Using the factor 1 mol/44.01 g:

moles CO2 = 454 g x 1 mol/44.01 g = 10.3 moles

Answer

There are 10.3 moles of CO2 in 454 grams of CO2.

Sometimes you're given a value in moles and need to convert it to grams. To do this, first calculate the molar mass of a sample. Then, multiply it by the number of moles to get an answer in grams:

grams of sample = (molar mass) x (moles)

Problem

Find the number of grams in 0.700 moles of hydrogen peroxide, H2O2.

Solution

Calculate the molar mass by multiplying the number of atoms of each element in the compound (its subscript) times the atomic mass of the element from the periodic table.

Molar mass = (2 x 1.008) + (2 x 15.999)Molar mass = 34.014 grams/mol

Multiply the molar mass by the number of moles to get the grams:

grams of hydrogen peroxide = (34.014 grams/mol) x (0.700 mol) = 23.810 grams

Answer

There are 23.810 grams of hydrogen peroxide in 0.700 moles of hydrogen peroxide.

Here is another example showing how to convert moles to grams.

Problem

Determine the mass in grams of 3.60 mol of H2SO4.

Solution

First, look up the atomic masses for hydrogen, sulfur, and oxygen from the periodic table. The atomic mass is 1.008 for H, 32.06 for S, and 16.00 for O. The formula mass of H2SO4 is:

2(1.008) + 32.06 + 4(16.00) = 98.08

Thus, one mole of H2SO4 weighs 98.08 grams. This relation provides a conversion factor to go from grams to moles. Using the factor 98.08 g / 1 mol:

grams H2SO4 = 3.60 mol x 98.08 g / 1 mol = 353 g H2SO4

Answer

There are 353 grams of H2SO4 in 3.60 moles of H2SO4.

Here are some tips for performing these conversions. The two problems most commonly encountered are not cancelling the units correctly and using the incorrect number of significant figures.