How to know how many valence electrons are in an element

Which part of earth’s surface receives the most direct rays from the sun? a) equator b) ocean c) poles d) mountains

What is the mass of naoh that would have to be added to 500 ml of a solution of 0.20 m acetic acid in order to achieve a ph of 5.0?

Steam reforming of methane ( ch4) produces "synthesis gas," a mixture of carbon monoxide gas and hydrogen gas, which is the starting point for many important industrial chemical syntheses. an industrial chemist studying this reaction fills a 1.5 l flask with 3.5 atm of methane gas and 1.3 atm of water vapor at 43.0°c. he then raises the temperature, and when the mixture has come to equilibrium measures the partial pressure of carbon monoxide gas to be 1 .0 atm. calculate the pressure equilibrium constant for the steam reforming of methane at the final temperature of the mixture. round your answer to 2 significant digits.