June 2018 NY Regents Chemistry Exam

37 Given the equation representing a reaction: 2C + 3H2 → C2H6 What is the number of moles of C that must completely react to produce 2.0 moles of C2H6? (1) 1.0 mol

(2) 2.0 mol

(3) 3.0 mol

(4) 4.0 mol

Solution: The coefficients in the equation are 2 for C and 1 for C2H6 (if the coefficient is not shown, we can assume that it is 1). This means when 2 moles of C react they produce 1 mole of C2H6. Therefore, to produce 2.0 moles of C2H6, we would need twice the amount of C, which would be 2*2 = 4moles

Answer: 4

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