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Question 14 (2 points) Saved Naturally occurring copper exists in two isotopic forms: 63Cu and 65Cu. The atomic mass of copper is 63.55 amu. What is the approximate natural abundance of 63Cu? 63% 90% O 70% 50% 30% Question 15 (2 points) If 0.274 moles of a substance weighs 62.5 g, what is the molar mass of the substance, in units of g/mol? 2.17 x 102 g/mol 1.71 x 101 g/mol 6.02 x 1023 g/mol 2.28 x 102 g/mol 4.38 x 10-3 g/mol