Equations and Calculations
Number of moles = Mass(g) / Ar/Mr
2 HgO ----> 2Hg + O2
HgO = 117
a)What mass of Mercury (Hg) is formed from 21.7g of HgO?
Step1) Use mass/g from Q to find n.o of moles.
Number of moles of HgO = 21.7/217 = 0.1 moles of HgO
Step 2) Use the equation to find ratio to tell you how many moles of theone you are calculating.
0.1 moles HgO : 0.1 moles Hg
0.1 moles Hg : 0.05 moles O2
Step 3) Use number of moles from step2 and find mass/g of Hg.
0.1 = mass(g)/201 mass of Hg = 201*0.1=20.1Hg
21.7-20.1=1.6g of O2
0.05 = mass(g) / 32
Mass of O2/g = 32*0.05=1.6g