What is the hardest part of the periodic table?

Mercury metal is poured into a graduated cylinder that holds exactly 22.5 ml the mercury used to fill the cylinder mass in 306.0 g from this information calculate the density of mercury

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?

In a 28 g serving of cheese curls there are 247mg of sodium. how much sodium is in a 12.5 ounce bag