Which is a reason to use rate laws?
to investigate how the pressure of liquids affects reaction rates
to find the new rate when the concentration of reactants changes
to calculate the molecular weight of compounds in a reaction
to find the number of moles of solute that are dissolved in 1 l of solution

If a molecule with a molecular formula of c13h18 is treated with an excess of h2 in the presence of finally divided pt metal under conditions required for maximum hydrogenation of the molecule to give a molecule with a formula c13h24, how many rings are in the molecule?

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

What amount of heat is exchanged when 106.2 grams of substance y goes from a liquid at 35 degrees celsius to a solid at the same temperature? melting point of substance y = 35 degrees c; δhvaporization = 3.67 j/mol; δhfusion = 3.30 j/mol. mwsubstance y = 28.22 g/mol. −12.4 j −3.51 x 102 j 1.24 x 101 j 351 j