Answer asap for 1.what does "excess reactant"mean? 2.what is percent yield?

Astudent is given a sample of a blue copper sulfate hydrate. he weighs the sample in a dry covered porcelain crucible and got a mass of 23.875 g for the crucible, lid, and sample. the mass of the empty crucible and lid was found earlier to be 22.652 g. he then heats the crucible to expel the water of hydration, keeping the crucible at red heat for 10 minutes with the lid slightly ajar. on colling, he finds the mass of crucible, lid, and contents to be 23.403 g. the sample was changed in the process to very light clue anhydrous cuso4. if there are again 100.0 g of hydrate, how many grams of cuso4 are in it? how many moles of cuso4? (hint: molar mass of cuso4 = 159.6 g / mole. what per cent of the hydrate is cuso4? you may convert the mass of cuso4 to moles.)

Calculate the standard enthalpy of formation of liquid methanol, ch3oh(l), using the following information: c(graphite) + o2 latex: \longrightarrow ⟶ co2(g) latex: \delta δ h° = –393.5 kj/mol h2(g) + o2 latex: \longrightarrow ⟶ h2o(l) latex: \delta δ h° = –285.8 kj/mol ch3oh(l) + o2(g) latex: \longrightarrow ⟶ co2(g) + 2h2o(l) latex: \delta δ h° = –726.4 kj/mol

The combustion of methane, ch4, releases 890.4kj/mol. that is, when one mole of methane is burned,890.4 kj are given off to the surroundings. this meansthat the products have 890.4 kj less than the reactants.thus, ah for the reaction = - 890.4 kj. a negative symbolforah indicates an exothermic reaction.ch (g) + 20 (g)> co2 (g) + 2 h0 (1); ah = - 890.4 kga) how much energy is given off when 2.00 mol of ch,are burned? b) how much energy is released when 22.4g of ch. areburned?