1. What is the molar mass of Na2SO410H2O?
QUESTION:
What is the molar mass of Na2SO410H2O?
A g/mol, B g/mol C g/mol
Definition: Molar mass = mass per mole
Look up molar masses from periodic table.
One mole of Na2SO410H2O contains
One mole Na2SO4 and 10 moles H2O.
One mole Na2SO4 contains
2 mol Na: 2 mol Na x g/mol = g
1 mol S: mol S x g/mol = g
4 mol O: mol O x g/mol = g
Total mass of one mole of Na2SO4 = g
One mole H2O has a mass of g
10 moles H2O has a mass of g
Total mass of one mole Na2SO410H2O is g.
What is the molar mass of sodium sulfate decahydrate?
A g/mol, B g/mol C g/mol
PAUSE CLICK
The term molar mass refers to the mass of one mole of anything.
Molar masses of atoms can be easily looked up from a periodic table.
CLICK
For example, in a typical periodic table, the average mass of sodium atoms in nature is given as atomic mass units.
HIGHLIGHT 22.99
A mole is defined such that the mass in grams of one mole of sodium is also
Some periodic tables may give more significant figures. For most calculations, it is usually more than sufficient to keep only
four significant figures for molar masses of atoms.
One mole of this compound contains one mole of the formula shown to the left of the dot
HIGHLIGHT Na2SO4 in Na2SO410H2O
and 10 moles of H2O
HIGHLIGHT 10 in the formula.
Based on the subscripts in the formula of the compound, we can say that
one mole of sodium sulfate contains
CLICK two moles of sodium since the subscript of sodium in the formula is implied to be 2.
Two moles of sodium times grams per mole is equal to grams.
Therefore, one mole of sodium sulfate contains two moles of sodium, or grams
CLICK Similarly, one mole of sodium sulfate contains one mole of sulfur, or grams
and 4 moles of oxygen
HIGHLIGHT 4 in Na2SO4
or grams of oxygen
Adding up these masses, we get a total mass of grams for one mole of Na2SO4.
Using the same procedure, we can calculate that one mole of H2o has a mass of grams.
CLICK Therefore, 10 moles of H2O times grams per mole, equals grams.
CLICK Thus, the total mass of one mole of sodium sulfate decahydrate is equal to
the mass of one mole of Na2SO grams
plus the mass of ten moles of H2O grams
which equals grams.
The molar mass of sodium sulfate decahydrate is grams per mole.
The correct answer is B.
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2. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08