Copper has two naturally occurring isotopes, copper-63 and copper-65. A sample of copper contains 69.15% of copper-63 and 30.85% of copper-65. Calculate the relative atomic mass (ArA_rAr) of copper in this sample. Give your answer to two decimal places. You must show your working.
87 exam-style questions on Edexcel GCSE Chemistry 2.1 Atomic structure, covering 2.1.1 Development of the atomic model, 2.1.2 Structure of the atom and subatomic particles, 2.1.3 Mass number, isotopes and relative atomic mass, and 2.1.4 Calculating relative atomic mass from isotopic abundance. Each one has a worked solution and a mark scheme showing where the marks go.