June 2023 NY Regents Chemistry Exam
37 What is the number of moles in a 78.8-gram sample of MgCO3 (gram-formula mass 84.3 g/mol)? (1) 0.949 mol
(2) 0.935 mol
(3) 0.843 mol
(4) 1.070 mol
Solution: Table T on the Reference Table gives the equation for calculating moles which is number of moles = given mass/ gram formula mass. All we need to do is to plug our values in.
Moles = 78.8g/84.3 g/mol
Answer: 2
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