A research group must generate a small amount of Ag2CrO4(s) as a colorimetric indicator by adding 0.200 M K2CrO4 solution to 500 mL of 0.0100 M AgNO3. The precipitation should begin only after the K2CrO4 solution has been added; no solid should be present initially. The solubility product of Ag2CrO4 at 25 °C is Ksp=1.1×10−12. Assume volumes are additive and temperature remains constant.
(a) Derive an equation that relates the volume V (in mL) of 0.200 M K2CrO4 added to the ionic concentrations present immediately after mixing with the 500 mL AgNO3 solution.
(b) Using the relationship from part (a), calculate the minimum volume of 0.200 M K2CrO4 that must be added for Ag2CrO4(s) to begin to form.
(c) After adding the calculated volume from part (b), the researchers mistakenly double the amount of K2CrO4 added. Assuming no further volume change except the extra addition, determine the mass of Ag2CrO4(s) that will precipitate as a result of the error. Express your answer in milligrams.
(d) Evaluate whether the common-ion effect would make it easier or more difficult to redissolve the precipitate formed in part (c) by adding excess NH3(aq). Support your answer with an explanation based on equilibrium principles.