Which equation shows a physical change?

pb(no3)2 (aq) + 2ki(aq) _ 2kno3(aq) + pbi2(s)

hcl(aq) + naoh(aq) _ nacl(aq) + h2o(l)

2h2o(l) _ 2h2(g) + o2(g)

h2o(g) _ h2o(s)

Classify each statement about effective nuclear charge, zeff, as true or false.

An exothermic reaction is conducted in an insulated calorimeter filled with water. the calorimeter is then sealed so that there is no heat exchanged between the contents of the container and the surrounding air. which of the following statements is true about the reaction?

Determine the wavelength of the light absorbed when an electron in a hydrogen atom makes a transition from an orbital in the n=3 level to an orbital in the n=7 level.