The mole

Molar Mass

Recall The term “Avogadro’s Number” was coined by Jean Baptiste Perrin when he determined the number of atoms in one gram of atomic hydrogen And he figured out that 1 gram of hydrogen has 6.022x1023 atoms Remember: 6.022x1023 atoms = 1 mole Which means that 1 mole of hydrogen has a mass of 1 gram

Recall Also remember that atomic mass is measured in atomic mass units (amu) 1 amu = 1/12 mass of a carbon atom Going back to Avogadro, based on Avogadro’s Law there are 6.022x1023 atoms in 12 grams of C-12 Basically, look at the number of amu on the periodic table = Number of grams per mole for that element

Atomic Molar Mass (MM) MM of C = 12.01 g/mol What is molar mass? The mass (g) of 1 mole of atoms of a particular element or molecule → The mass (g) of 6.02 X 1023 atoms or particles How do you figure out molar mass? Find on periodic table MM of H = 1.01 g/mol MM of C = 12.01 g/mol

practice 14.01 g/mol 87.62 g/mol 55.85 g/mol 26.98 g/mol What is the molar mass of the following elements? Nitrogen: Strontium: Iron: Aluminum: 14.01 g/mol 87.62 g/mol 55.85 g/mol 26.98 g/mol

Calculations with Molar Mass molar mass (g/mol) Mass (g) n (mol)

practice 1 mol Al = 26.98g 3 mol Al = 26.98g x 3.00 = 80.9 g Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al? 3.00 moles Al ? g Al 1 mol Al = 26.98g 3 mol Al = 26.98g x 3.00 = 80.9 g

Everything must go through Moles!!! Calculations molar mass (g/mol) Avogadro’s number (6.02 X 1023 particles/mole) mass (g) n (mol) particles Everything must go through Moles!!!

Let’s combine it all!

practice 𝑚𝑎𝑠𝑠 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 =# 𝑚𝑜𝑙𝑒𝑠 1 mol Cu = 63.546 g How many atoms of Cu are present in 35.4 g of Cu? 1 mol Cu = 63.546 g 6.023𝑥1023 𝑎𝑡𝑜𝑚𝑠 1 𝑚𝑜𝑙𝑒 = ?𝑎𝑡𝑜𝑚𝑠 0.557 𝑚𝑜𝑙𝑒𝑠 63.546 𝑔 𝐶𝑢 1 𝑚𝑜𝑙𝑒 = 35.4 𝑔 𝐶𝑢 ? 𝑚𝑜𝑙𝑒𝑠 ? = 3.35x1023 atoms ? = 0.557 mol 𝑚𝑎𝑠𝑠 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 =# 𝑚𝑜𝑙𝑒𝑠 # 𝑚𝑜𝑙𝑒𝑠 𝑥 6.022𝑥 10 23 =# 𝑎𝑡𝑜𝑚𝑠

practice 𝑚𝑎𝑠𝑠 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 =# 𝑚𝑜𝑙𝑒𝑠 1 mol K = 39.0983 g How many atoms of K are present in 78.4 g of K? 1 mol K = 39.0983 g 6.023𝑥1023 𝑎𝑡𝑜𝑚𝑠 1 𝑚𝑜𝑙𝑒 = ?𝑎𝑡𝑜𝑚𝑠 2.00 𝑚𝑜𝑙𝑒𝑠 39.0983 𝑔 𝐾 1 𝑚𝑜𝑙𝑒 = 78.4 𝑔 𝐾 ? 𝑚𝑜𝑙𝑒𝑠 ? = 1.25x1024 atoms ? = 2.00 mol 𝑚𝑎𝑠𝑠 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 =# 𝑚𝑜𝑙𝑒𝑠 # 𝑚𝑜𝑙𝑒𝑠 𝑥 6.022𝑥 10 23 =# 𝑎𝑡𝑜𝑚𝑠

Molecular Molar Mass (MM) Mass in grams of 1 mole equals the sum of the atomic masses H2 H20 2 x (MM of H) = 2(1.01g/mol) = 2.02g/mol (2 x (MM of H)) + (MM of O) = 2(1.01g/mol) + (16.00g/mol) = 18.02 g/mol)

Practice CH3OH Al2(SO4)3 (1 x MM of C) + (4 x MM of H) + (1 x MM of O) = 12.01g/mol + (4 x (1.01g/mol) + 16.00g/mol) = 32.05 g/mol (2 x MM of Al) + (3 x MM of S) + (12 x MM of O) = (2 x 26.98g/mol) + (3 x (32.06g/mol) + (12 x16.00g/mol) = 342.14 g/mol

Ready for a challenge?

practice 1)Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass. (17 x MM of C) + (18 x MM of H) + (3 x MM of F) + (1 x MM of N) + (1 x MM of O) = (17 x 12.01g/mol) + (18 x 1.01g/mol) + (3 x19.00g/mol) + (1 x 14.01g/mol) + (1 x16.00g/mol) = 309.36 g/mol

The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame? Step 1 – Calculate molar mass (14 x MM of C) + (18 x MM of H) + (2 x MM of N) + (5 x MM of O) = (14 x 12.01g/mol) + (18 x 1.01g/mol) + (2 x 14.01g/mol) + (5 x16.00g/mol) = 294.34 g/mol Step 2 – Calculate # moles 𝑚𝑎𝑠𝑠 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 =# 𝑚𝑜𝑙𝑒𝑠 = 225𝑔 294.23𝑔/𝑚𝑜𝑙 = 0.764 𝑚𝑜𝑙

= 180.18 g/mol = (6 x 12.01g/mol) + (12 x 1.01g/mol) + (6 x16.00g/mol) What is the mass (in grams) of 1.20 X 1024 molecules of glucose (C6H12O6)? Step 1 – Calculate molar mass (6 x MM of C) + (12 x MM of H) + (6 x MM of O) = (6 x 12.01g/mol) + (12 x 1.01g/mol) + (6 x16.00g/mol) = 180.18 g/mol Step 2 – Calculate # moles Step 3 – Calculate mass # 𝑎𝑡𝑜𝑚𝑠 6.022𝑥 10 23 =# 𝑚𝑜𝑙𝑒𝑠 𝑚𝑎𝑠𝑠=𝑛 𝑥 𝑀𝑀 = (1.99 mol)(180.18 g/mol) = 1.20𝑥 10 24 6.022𝑥 10 23 = 1.99 𝑚𝑜𝑙 = 359𝑔

= 32.00 g/mol # 𝑚𝑜𝑙𝑒𝑠 𝑥 6.022𝑥 10 23 =# 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒𝑠 How many molecules of oxygen gas, O2, are present in 78.1 g of O2? Step 1 – Calculate molar mass Step 3 – Calculate # molecules = (2 x MM of O) # 𝑚𝑜𝑙𝑒𝑠 𝑥 6.022𝑥 10 23 =# 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒𝑠 2.44 𝑥 6.022𝑥 10 23 =# 𝑚𝑜𝑙𝑒𝑐𝑢𝑙𝑒𝑠 = (2 x16.00g/mol) =1.48 𝑥 6.023𝑥 10 24 = 32.00 g/mol Step 2 – Calculate # moles 𝑚𝑎𝑠𝑠 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 =# 𝑚𝑜𝑙𝑒𝑠 = 78.1𝑔 32.00𝑔/𝑚𝑜𝑙 = 2.44 𝑚𝑜𝑙