Iodine is 80% 127I, 17% 126I, and 3% 128I. Calculate the average atomic mass of iodine.

Enough of a monoprotic weak acid is dissolved in water to produce a 0.0172 m solution. if the ph of the resulting solution is 2.39 at 20 °c, determine the pka for the acid.

If 1.63 times 10 negative 4 of helium dissolves in 100.0g of water, what is the concentration in parts per million

3. how much energy in joules is required to evaporate .0005 kg of liquid ammonia to vapor at the same temperature? 4. how much energy ( in megajoules ) is given up by .75 kg of water at 0c when it freezes to form ice at 0c? 5. explain how heat works between and at critical temperatures?