Question

What is the mass, in grams, of 1.30 molmol of water, H2OH2O?

Learning Goal: Be able to convert to mass from a given number of moles. Completing problems such as this is critical for ensuring your success in chemistry. If you would like to get a head start (and we strongly suggest you do if you want to do well in the course) we have provided you with help to learn this concept in the hints. Hints for this problem contain a digital video for a similar problem, and a series of steps to help you solve this problem. The mole is a chosen amount, or count of something. This number, or count, is 6.02 x 104 units The mole (abbreviated mol) is a counting unit used by chemists to help simplify calculations that involve atoms, because the number of atoms in everyday items is very large since atoms themselves are so small. This number, named to honor the scientist Amadeo Avogadro, is 6.022 x 1023. This value was chosen because it equaled the number of carbon atoms in exactly 12 g of isotopically pure 12C. Thus, there are exactly 6.022 x 104 atoms of carbon, or 12 grams of carbon, in one mole of carbon-12. A mole of carbon is large enough to be weighed on a laboratory scale which makes it simpler to work with moles in a typical laboratory setting. One mole of any substance contains 6.022 x 1023 formula units. This choice allows chemists to use the atomic mass numbers on the periodic table as the number of grams per mole for each element. For example carbon-12 has an atomic mass of 12.0 atomic mass units on the periodic table. Also, one mole of carbon atoms has a mass of 12.01 grams (not 12.00 because there are other isotopes that weigh more than carbon-12 that are much less common). Thus, to convert from grams to moles, you can use the masses from the periodic table to construct a conversion factor. For example: 12.01 g/ 1 mole of carbon. The mole allows the same to be done for molecules. 1 mole of water molecules, H20, equals the additive atomic masses for two hydrogen atoms and one oxygen atoms, in grams. Thus the mass of one mole of water (rounded to two significant digits) is 1.0 gram + 1.0 gram + 16 grams = 18 grams per one mole. The number of grams in one mole is called the molar mass. The molar mass of water is 18 g/mol to two significant digits. Watch this video for an additional explanation.

Answer 1

According to mole concept. 1mol atoms/molecules has mass equal to the atomic/molar mass in grams

So Here , for 1 mol H2O has mass = molar mass in grams'

molar mass of H2O = 18 g [given in the above paragraph]

1 mol H2O has mass= 18 g
then
1.30 mol H2O has mass= 1.30 mol* 18 g/mol = 23.4 g

Answer: 23.4 g
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