Is a burning log an exothermic or endothermic event if the log is the system?

After cloud droplets form, what must happen to them for precipitation to occur?

In this chemical reaction, 325 grams of barium (ba) react completely. how many moles of lithium (li) are produced?

Consider the reaction: 2al(s) + fe2o3(s) → al2o3(s) + 2fe(s) the δhf for fe2o3(s) = -824.3 kj/mole. the δhf for al2o3(s) = -1675.7 kj/mole. finish the equation. δhrxn = [(1)( kj/mole) + (2)( kj/mole)] - [(1)( kj/mole) + (2) ( kj/mole)]