At elevated temperatures, NaHCO3 is converted quantitatively to NazCO3: 2 NaHCO:(s) → NazCO3 (s) + CO2 (g) + H20 (g). Ignition of a 0.6239-g sample of an antacid tablet containing NaHCO3 and nonvolatile impurities yielded a residue weighing 0.4129 g. Calculate the percent purity of the antacid sample. Some helpful FW: NaHCO3 = 84.01 ; Na2C03 = 105.99 ; CO2 = 44.01 ; H2O = 18.02

QUESTION 30 Which statement best explains the toxicity of trivalent lanthanide cations to plant life O The lanthanide ion replaces calcium in the oxygen evolving centre and the resulting hydroxide intermediate is not sufficiently nucleophilic to attack the transient manganyl(v) species in the S4 state O The lanthanide ion replaces calcium in the oxygen evolving centre and the resulting aqua intermediate is not sufficiently acidic to generate a hydroxide intermediate O The lanthanide coordinates to pheophytin disrupting the electron transport chain O The lanthanide ion replaces magnesium in the P680 causing a shift in its redox potential O The lanthanide cation precipitates chloride from the active site of the oxygen evolving centre

Fe3+(aq)  +  SCN–(aq)    ⇆   FeSCN2+(aq) Suppose that the solution of NaSCN was accidentally prepared using too much solid NaSCN, so that that solution had a higher [SCN-] value than expected.   How would the resulting measured Keq value differ from the true Keq value:  too large, too small, or unaffected? Explain

If the concentration of an acid in solution is 2.2 times larger than the concentration of its conjugate base, and the pH of the solution is 3.5, what is the pKa of the acid? Include the answer to 3 significant figures