Shopping for a gift at a Rock and Mineral store, you find a nice red rhodonite (MnSiO3) crystal, but it is a bit dirty. The clerk offers to soak it in one of two cleaning solutions for you.
Solution 1: Water with a pH of 6
Solution 2: Water of pH 11 with excess quartz
You are worried that the crystal may dissolve. You find the following relevant reactions and answer the following a, b and c below.
MnSiO3(s) > Mn2++ SiO32
HSiO3(aq) > HSiO3+H+
HSiO3 > SiO2-+ H+
SiO2 (s)(quartz)+ H2O) > H2SiO3(aq)
Kso = 10-11.79
Ka1 = 10-9.90
Ka2 = 10-13.2
Kso = 10-2.69
Mn2++ H,O >MnOH++ H+
Mn2++ 3H2O >Mn(OH)3+ 3H+
Mn2++ 4H,O >Mn(OH)42-+ 4H+
* = 10-10.6
*B3 = 10-34.8
*4 = 10-48.3
a. Assuming there is excess rhodonite present, what is the total dissolved concentrations of manganese (Mnt) for Solution 1? Assume that quartz does not precipitate
b. Assuming there is excess rhodonite present, what is the total dissolved concentrations of manganese (Mnt) for Solution 2? Assume that the SiO32- released from the MnSiO3(s) is negligible compared to that produced by quartz. Comment on the validity of this assumption after performing your calculation. Hint: Common ion effect
C. Which cleaning solution will you choose based on your calculation?