From 1962 until 1981 pennies were made from 95% copper and 5% zinc and had a mass of 3.1 g. Starting in 1982, pennies have been made from 97.5% zinc and 2.5% copper and have a mass of 2.5 g. Suppose you have a sample of pennies that consists of 45.4% pre-1982 pennies. Determine the average mass of a penny in this sample.

  the mississippians were considered to be  horticulturalists, which means they were

Percent ionization for a weak acid (ha) is determined by the following formula: percent ionization=[ha] ionized[ha] initial×100%for strong acids, ionization is nearly complete (100%) at most concentrations. however, for weak acids, the percent ionization changes significantly with concentration. the more diluted the acid is, the greater percent ionization.a certain weak acid, ha, has a ka value of 9.4×10? 7.part acalculate the percent ionization of ha in a 0.10 m solution.part bcalculate the percent ionization of ha in a 0.010 m solution

Which of the four hypothetical substances you investigated would be most harmful to living organisms? 50 points!