How many hydrogen molecules are in 2.75 L of H2 gas at STP

Which statement is usually true about the relationship between activation energy and reaction rates? low activation energy barriers result in low rates. high activation energy barriers result in low rates. low activation energy barriers result in no reaction. high activation energy barriers result in no reaction.

2pos suppose an object in free fall is dropped from a building. its starting velocity is 0 m/s. ignoring the effects of air resistance, what is the speed (in m/s) of the object after falling 3 seconds? give your answer as a positive decimal without units. answer here

Answer asap : ( a. how does mucus prevent the entry of pathogens? b. describe two ways white blood cells protect us from pathogens.