Worksheet 5 – Solutions, Electrolytes and Concentration
The name electrolyte is given to substances whose aqueous solutions contain
ions, because ions are charged particles which, when they move through a
solution, conduct electricity.
Strong electrolytes dissociate completely into ions. This includes the strong
acids (HCl, HBr, HI, HNO3, HClO4 and H2SO4). HF and other acids are
considered weak acids.
The strong bases (LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2 and
Ba(OH)2) dissociate completely. Most salts (except HgCl2 and Hg(CN)2) are
Weak electrolytes do not dissociate completely into ions. This includes most
acids and bases, except those listed above.
Non-electrolytes are species which dissolve in water, but which do not
dissociate. Soluble covalent compounds are covalent compounds like glucose
1. Categorize each of the following compounds:
compound acid, base, salt electrolyte products
molecule non-, weak, strong
Units of Concentration - Molarity is a measure of the number of moles of solute
per 1. L of solution. It is given the symbol M and has units of mol/L.
1. A bottle is labeled as 2.5 M Ca(OH)2.
a. What is the concentration of Ca2+(aq)?
b. What is the concentration of OH- (aq)?
c. When you measure out 250 mL of this solution, how many moles of
Ca2+ and OH- will be present?
d. How many grams of Ca2+ and OH- will be present in 250 mL?
e. We now add enough water to give a total volume of 1.00L. What is
the concentration of Ca(OH)2 in this solution.
2. How many grams of NaOH must be weighed out to make 250.0 mL of a
0.100 M solution of NaOH?
a. Start with what you know, the final volume and concentration of the
solution. Arrange these factors to calculate the moles of NaOH
b. Change moles of NaOH to grams of NaOH.
3. Calculate the molarity of a solution of CO2 in water, which contains 0.145
g of CO2 per 100. mL of solution.
4. What are the molarities of the ions in the following mixture?
50.00 mL of 0.100 M CuSO4 mixed with 200.0 mL of 0.040 M K2SO4?
a. Calculate the number of moles of Cu2+ and SO42- from the first
b. Calculate the number of moles of K+ and SO42- from the second
c. Calculate the volume of the mixture.
d. Calculate the molarity of all of the species in solution.
5. How would you prepare 2.00 L of a 0.250 M solution of NaOH from a 1.00
M stock solution of NaOH?
Hint: moles of solute before dilution = moles of solute after dilution
6. How would you prepare:
1.00 L of a 0.400 M solution of H2SO4 from 18 M stock
500. mL of a 1.00 M solution of HCl from 12 M stock
3.00 L of 5.00 M HNO3 from 16 M stock
7. How many moles of ions are present in 250. mL of a 0.15 M Na2SO4
8. When 50.0 mL of 0.20 M Na2CO3 are combined with 30.0 mL of 0.50 M
NaCl, what is the concentration of ions in this solution?