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Chemistry Mole Calculations

This document discusses mole calculations and stoichiometry problems. It explains that the number of moles can be calculated from mass and molar mass using the formula number of moles = mass/molar mass. It also shows how to calculate the number of particles, volume of gas, and concentration from the number of moles. Sample stoichiometry problems are provided to calculate masses, numbers of moles, and formulas from chemical equations.

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ashleytham89
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35 views16 pages

Chemistry Mole Calculations

This document discusses mole calculations and stoichiometry problems. It explains that the number of moles can be calculated from mass and molar mass using the formula number of moles = mass/molar mass. It also shows how to calculate the number of particles, volume of gas, and concentration from the number of moles. Sample stoichiometry problems are provided to calculate masses, numbers of moles, and formulas from chemical equations.

Uploaded by

ashleytham89
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPTX, PDF, TXT or read online on Scribd
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Mole calculations

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𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒𝑠=𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 × 𝐴𝑣𝑜𝑔𝑎𝑑𝑟 𝑜 𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡

𝑚𝑎𝑠𝑠(𝑖𝑛 𝑔𝑟𝑎𝑚𝑠) 𝑚𝑎𝑠𝑠(𝑖𝑛 𝑔𝑟𝑎𝑚𝑠)


𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠= OR 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠=
𝐴𝑟 𝑀𝑟

𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑔𝑎𝑠=𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 ×24 𝑑 𝑚 3

× 𝑀𝑟
𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝑚𝑎𝑠𝑠(𝑖𝑛 𝑔𝑟𝑎𝑚𝑠)
𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛=
𝑉𝑜𝑙𝑢𝑚𝑒 𝑉𝑜𝑙𝑢𝑚𝑒

÷ 𝑀𝑟
2 moles of H2 gas  2 moles of H2 molecules 23 24
2 ×6.02 ×10 =1.204 × 10 𝐻 2𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒𝑠
4 moles of H atoms 23 24
4 ×6.02 ×10 =2.408 × 10 h𝑦𝑑𝑟𝑜𝑔𝑒𝑛 𝑎𝑡𝑜𝑚𝑠

one H2 molecule contains 2 H atoms


Find number of hydrogen atoms in 5 moles of water molecule

10 moles of hydrogen atoms 

One water molecule contains 2 hydrogen atoms and 1 oxygen atom


𝑚𝑎𝑠𝑠= 𝐴𝑟 ×𝑛𝑜 .𝑜𝑓 𝑚𝑜𝑙𝑒𝑠=80 × 0.5=40 𝑔

𝑚𝑎𝑠𝑠 64
𝑛𝑜 . 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠= = =2 𝑚𝑜𝑙𝑒𝑠
𝑀𝑟 32
2 𝐻 2 +𝑂 2 →2 𝐻 2 𝑂

𝑚𝑎𝑠𝑠 1
𝑛𝑜 . 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝐻 2= = =0.5 𝑚𝑜𝑙𝑒𝑠
𝑀𝑟 2

𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑥𝑦𝑔𝑒𝑛=𝑛𝑜. 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠× 𝑀𝑟 =0.25 ×32=8 𝑔𝑟𝑎𝑚𝑠

𝑚𝑎𝑠𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 =1+8=9 𝑔𝑟𝑎𝑚𝑠


𝐹𝑒+𝐶𝑢𝑆𝑂 4 → 𝐹𝑒𝑆𝑂 4 +𝐶𝑢
𝑚𝑜𝑙𝑒 𝑟𝑎𝑡𝑖𝑜 𝑜𝑓 𝐹𝑒: 𝐶𝑢=1:1

𝑚𝑎𝑠𝑠 1.4
𝑛𝑜 . 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠𝑜𝑓 𝑖𝑟𝑜𝑛= = =0.025 𝑚𝑜𝑙𝑒𝑠
𝐴𝑟 56

𝑚𝑎𝑠𝑠 1.6
𝑛𝑜 . 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠𝑜𝑓 𝑐𝑜𝑝𝑝𝑒𝑟 = = =0.025 𝑚𝑜𝑙𝑒𝑠
𝐴𝑟 64

𝑇h𝑒𝑟𝑒𝑓𝑜𝑟𝑒 , 𝑡h𝑒 𝑓𝑜𝑟𝑚𝑢𝑙𝑎 𝑓𝑜𝑟 𝑖𝑟𝑜𝑛𝑠𝑢𝑙𝑓𝑎𝑡𝑒 𝑖𝑠 𝐹𝑒𝑆 𝑂 4


𝑇h𝑒 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑡h𝑒 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑𝑖𝑠 62.1 , 𝑤h𝑎𝑡 𝑖𝑠 𝑡h𝑒𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑓𝑜𝑚𝑟𝑢𝑙𝑎𝑜𝑓 𝑡h𝑒 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑?

Carbon Hydrogen Oxygen

% by mass 38.7 9.75 51.55

Ar 12 1 16

Mole (mass/Ar) 38.7/12 = 3.23 9.75/1=9.75 51.55/16=3.22

Ratio (divide by 3.23/3.22 ≈ 1 9.75/3.22 ≈ 3 3.22/3.22 = 1


smallest number)

𝑇h𝑒𝑟𝑒𝑓𝑜𝑟𝑒 , 𝑡h𝑒 𝒆𝒎𝒑𝒊𝒓𝒊𝒄𝒂𝒍 𝒇𝒐𝒓𝒎𝒖𝒍𝒂 𝑖𝑠 𝐶 𝐻 3 𝑂

= 12 + 3(1) + 16 = 31
62.1
≈ 2 𝑠𝑜 𝑡h𝑒 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑓𝑜𝑟𝑚𝑢𝑙𝑎 ( 𝑎𝑐𝑢𝑡𝑎𝑙 ) 𝑖𝑠 𝐶 2 𝐻 6 𝑂 2
31

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