All AP Chemistry Resources
Example Questions
Example Question #411 : Ap Chemistry
What volume of water must be added to 750mL of 0.050M sodium chloride () in order to achieve a final concentration of 0.015M?
For a solution of known volume and concentration (molarity in this case), the volume needed to dilute the solution to a desired concentration may be found using the formula:
Where and are the initial and final concentrations, and and are the initial and final volumes. So, for 750mL (0.750L) of a 0.050M solution diluted to 0.015M:
Solving for :
Now that we know the total volume needed, we may find the volume that must be added by subtracting the initial volume () from the final volume ():
1.75L of water must be added to 750mL of 0.050M in order to achieve a final concentration of 0.015M
Example Question #51 : Solutions
What is the pH of a 0.025M solution of hydrochloric acid ()?
Since is a strong acid, calculations should be carried out assuming that the compound dissociates completely:
and are produced in a 1:1 ratio to total dissolved , so the concentration of in solution is the same as the concentration of :
pH is related to the concentration of :
Example Question #97 : Solutions And States Of Matter
What is the osmotic pressure of a 5.0M solution of at ?
Osmotic pressure is represented by:
Where Van’t hoff factor, , gas constant , temperature in . The Van’t hoff factor is a unitless number that represents the amount of ionic species that the compound will dissociate in solution. is part of a large group of molecules classified as hydrocarbons which normally do not dissociate at all in solution. Therefore, .
Plug in known values and solve.
Example Question #98 : Solutions And States Of Matter
A solution was prepared by dissolving 22.0 grams of in water to give a 110mL solution. What is the concentration in molarity of this solution?
In order to calculate the concentration, we must use molarity formula:
We must use the molecular weight of to calculate the moles of solute:
Example Question #411 : Ap Chemistry
A solution was prepared by dissolving 40.0 grams of in water to give a 50mL solution. What is the concentration in molarity of this solution?
In order to calculate the concentration, we must use molarity formula:
We must use the molecular weight of to calculate the moles of solute:
Example Question #91 : Solutions And States Of Matter
How many milliliters of solution is needed to dissolve 5 grams of to prepare a solution of concentration 10M?
In order to calculate the number of milliliters, we must first determine the number of moles in 5 grams of using its molecular weight as a conversion factor:
Using the concentration units as a conversion factor and the number of moles calculated, the number of milliliters can be calculated:
Example Question #11 : Other Solution Concepts
A solution was prepared by diluting 10mL of a 0.500M salt solution to 20mL. What would be the final concentration of this solution?
Use the dilution formula:
Rearranging this equation gives:
Plugging in the values gives:
Therefore, after diluting the solution to 20mL, the solution concentration would be lowered from 0.50M to 0.25M.
Example Question #412 : Ap Chemistry
Which of the following is a weak electrolyte?
Solutes that dissociate completely in a solution are called strong electrolytes. Weak electrolytes stay paired to some extent in solutions. As a result, strong electrolytes include ionic compounds and strong acid and bases.
Example Question #13 : Other Solution Concepts
Which of the following definitions is false?
Solubility product, , is the product of ion concentrations at equilibrium in a supersaturated solution of salt.
Ion-product constant of water, , is the product of equilibrium concentration of and ions in an aqueous solution at .
Molality is the number of moles of solute in a solution divided by the number of kilogram of solvent.
The van't Hoff factor, i, is the number of ions that a compound produces in a solution.
Solubility product, , is the product of ion concentrations at equilibrium in a supersaturated solution of salt.
Solubility product, , is the product of ion concentrations at equilibrium in a saturated solution of salt. All other definitions are true.
Example Question #413 : Ap Chemistry
Balance the following equation:
NaOH + H2SO4 → H2O + Na2SO4
2 NaOH + H2SO4 → H2O + Na2SO4
2 NaOH + H2SO4 → 2 H2O + Na2SO4
NaOH + H2SO4 → H2O + Na2SO4
4 NaOH + 2 H2SO4 → 4 H2O + 2 Na2SO4
4 NaOH + H2SO4 → 2 H2O + 2 Na2SO4
2 NaOH + H2SO4 → 2 H2O + Na2SO4
Balancing equations:
there is 1 NaOH and 1 H2SO4 in the reactants; and 1 H2O and 1 Na2SO4 in the products
steps:
1) balance the Na first; get 2 NaOH
2) balance H next; get 1 H2SO4, 2 H2O
3) check to make sure that O and S balance