How can I convert 12g of oxygen gas and 20g of water into moles?  

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For both of these calculations, you will need to use the conversion factor "1 mole = molar mass". So, before we begin the mole conversion calculations, we will need to calculate the molar masses of oxygen (` ` ) and water (` ` ).

Calculation of Molar Masses:

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For both of these calculations, you will need to use the conversion factor "1 mole = molar mass". So, before we begin the mole conversion calculations, we will need to calculate the molar masses of oxygen (` ` ) and water (` ` ).

Calculation of Molar Masses:

The molar mass of a substance is calculated by multiplying the atomic mass of each element in the substance by its subscript and then adding the resulting answers together. The atomic masses of oxygen (O) and hydrogen (H) can be found in the periodic table: atomic mass of oxygen (O) = 16.0 g; atomic mass of hydrogen (H) = 1.0 g

molar mass of`~O_2`: 2 x 16.0 g = 32.0 g

So, the conversion factor that we will use for the `~O_2` mole conversion calculation becomes: 1 mol = 32.0 g

molar mass of ` ` : (2 x 1.0 g) + (1 x 16.0 g) = 18.0 g

So, the conversion factor that we will use for the `~H_2O` mole conversion calculation becomes: 1 mol = 18.0 g

Mole Conversion Calculations:

To convert a substance in grams to moles, multiply the given amount of the substance times its conversion factor.

   12 g ` ` x (1 mol/32.0 g) = 0.38 mol `~O_2`

   20 g `~H_2O ` x (1 mol/18.0 g) = 1.1 mol `~H_2O`

Notice that in both calculations, the conversion factors are oriented such that the "gram part" of each conversion factor is in the denominator. This enables us to cancel out the gram units, leaving our answers in moles.

 

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