Chemistry Practice Quiz Solutions
1) average atomic mass for Li = [(mass Li-6)x(% Li-6)] + [(mass Li-7)x(% Li-7)]
average atomic mass for Li = [(6.0151223 amu)x(0.075)] + [(7.0160041)x(0.925)]
average atomic mass for Li = 6.9409380 amu
2) average atomic mass for B = [(mass B-10)x(% B-10)] + [(mass B-11)x(% B-11)]
average atomic mass for B = [(10.0129371 amu)x(0.199)] + [(11.0093055 amu)x(0.801)]
average atomic mass for B = 10.8110282 amu
3) average atomic mass for Cl from periodic table = 35.45
(mass 2nd isotope of Cl = A)
35.45 = [(mass Cl-35)x(% Cl-35)] + [(mass 2nd isotope Cl)x(% 2nd isotope Cl)]
35.45 = [(34.96885271 amu)x(0.7578)] + [(A)x(0.2422)]
35.45 = [(26.49939658)] + [(0.2422A)]
Subtract 26.49939658 from both sides of the equal sign
8.950603 = [(0.2422A)]
Divide 0.2422A from both sides of the equal sign
36.95542 = A = mass 2nd isotope of Cl
4) average atomic mass for Mg = [(mass Mg-24)x(% Mg-24)] + [(mass Mg-25)x(% Mg-25)] + [(mass Mg-26)x(% Mg-26)]
average atomic mass for Mg = [(23.9850419 amu)x(0.7899)] + [(24.9858370 amu)x(0.1000)] + [(25.9825930 amu)x(0.1101)]
average atomic mass for Mg = 24.3050518 amu
1) average atomic mass for Li = [(mass Li-6)x(% Li-6)] + [(mass Li-7)x(% Li-7)]
average atomic mass for Li = [(6.0151223 amu)x(0.075)] + [(7.0160041)x(0.925)]
average atomic mass for Li = 6.9409380 amu
2) average atomic mass for B = [(mass B-10)x(% B-10)] + [(mass B-11)x(% B-11)]
average atomic mass for B = [(10.0129371 amu)x(0.199)] + [(11.0093055 amu)x(0.801)]
average atomic mass for B = 10.8110282 amu
3) average atomic mass for Cl from periodic table = 35.45
(mass 2nd isotope of Cl = A)
35.45 = [(mass Cl-35)x(% Cl-35)] + [(mass 2nd isotope Cl)x(% 2nd isotope Cl)]
35.45 = [(34.96885271 amu)x(0.7578)] + [(A)x(0.2422)]
35.45 = [(26.49939658)] + [(0.2422A)]
Subtract 26.49939658 from both sides of the equal sign
8.950603 = [(0.2422A)]
Divide 0.2422A from both sides of the equal sign
36.95542 = A = mass 2nd isotope of Cl
4) average atomic mass for Mg = [(mass Mg-24)x(% Mg-24)] + [(mass Mg-25)x(% Mg-25)] + [(mass Mg-26)x(% Mg-26)]
average atomic mass for Mg = [(23.9850419 amu)x(0.7899)] + [(24.9858370 amu)x(0.1000)] + [(25.9825930 amu)x(0.1101)]
average atomic mass for Mg = 24.3050518 amu