What is the concentration of hydrogen ions commonly expressed as

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.

Find the mass, in grams, of 5.00*10^23 molecules of f2

Identify the lewis base in this balanced equation: fe3+ h2o fe(h2o)63+