Select all of the following that have a standard enthalpy of formation equal to zero at 25°C and 1.0 atm?
Si (s)
H20 (1)
N2 (g)
Al (s)
CH4 (g)
H2O(g) Br2 (l)

What is the overall order of reaction for rate = k[no2]2 ? second order 3/2 order third order zero order none of the listed answers are correct

Which statement best describes the relationship between period and frequency of light waves? a) in wave b the period increases and the frequency decreases from wave a. b) in wave a the period increases and the frequency decreases from wave b. c) in wave b the period is shorter and the frequency is greater than in wave a. d) in wave a the period is shorter and the frequency is greater than in wave b.

11. phosphorus-32 is radioactive and has a half life of 14 days. how much of a 124 mg sample of phosphorus-32 is present after 56 days? a) 7.75 mg b) 15.5 mg c) 31.0 mg d) 62.0 mg