Question

1. For an experiment, a biology student makes 1 liter of a solution containing the following substances, which are shown in the table below. Using the given information, fill in the missing parts of the table for each substance by (a) providing the formula weight and (b) calculating either the mass the student needs to weigh out or the number of moles that the student has, based on the amount weighed out. For each calculation, show your work. Be sure
to include the formula mass of water for CaCl2  2H2O and NaH2PO4  H2O.

Answer 1

This assignment simply tests your ability to relate the mass of chemicals to the amount of substance in mol though the use of the molar mass. So I will define the terms and give you the relation between the quantities and then you should be able to finish the problem your self:

Mass, \(m\), measured in gram for this purpose.

Amount of substance, \(n\), the amount of species in mol. The mol is just a number that simplify our work.

Molar mass, \(M\), is the mass of the species per mol. The unit therefore become g/mol. You calculate the molar mass by taking the sum of all the atomic weights of the atoms in molecule.
\[\large M=\sum_{i}M_i\]
For example for NaHCO3 it would look like this:
\[\large M(NaHCO_3)=M(Na)+M(H)+M(C)+3 \times M(O)\]


You can relate the mass, amount of substance and molar mass using the relation:
\[\Large m=M \times n\]
Depending on what you need to calculate (mass or amount of substance), you simply solve for that quantity.