There are two naturally occurring isotopes of boron. B-10 has a mass of 10.01 amu with an abundance of 19.80 % and the isotope B - 11 has a mass of 11.01 amu with an abundance of 80.20%. What is the atomic mass of boron? (Show work to get full credit)

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