Atoms Molecules Moles
September 11, 2022 2:57 PM
• Isotopic abundance: % by number of each of the isotopes of an element
• Mass defect: the difference between the combined masses of protons and neutrons an
the nucleus
○ Normally the atomic mass of an isotope has a fractional value close to the mass
§ C-12 is the only exception because its atomic mass is equal to exactly 12u
○ The mass defect and non-integer masses of protons and neutrons are why all iso
C-12 have irregular atomic masses
Moles:
• Mole: number of atoms in exactly 12 grams of pure C-12
○ This is Avogadro's number, NA, which is 6.02 x 1023 mol-1
• Number of particles (atoms/molecules/ions) = number of moles x NA
• 1 ATOM of carbon-12 has a mass of 12 u
• 1 MOLE of carbon-12 has a mass of 12g
• Molar mass is now MM, not just M
○ Molar mass and molecular mass have the same value but different units
§ Molecular mass is in AMU (u)
§ Molar mass is in g/mol
!"#$%& ()#(*%+ () , +-%./%+
• Mole fraction:
0(01* !"#$%& () #(*%+
○ To make it a percent just x100
Ex. Determine the mole fraction and the mole percent of NaCl and NaNO3 in a mixture of 0.2
NaCl and 0.3564 moles of NaNO3
Ex. Determine the mole fraction and mole percent of carbon in glucose (C6H12O6)
(34567 8 9 345:; 3:77 8) = (34567 > 9 345:; 3:77 >)
• Average molar mass of a mixture: MM =
0(01* #(*%+
Ex. A sample contains 0.187 mol of NaCl, 0.850 mol of CaCl2, and 1.250 mol of SiO2. Find the
mass of this mixture
,Solutions
September 11, 2022 7:33 PM
Molarity
• The number of moles of solute in 1L of the solution
• Molarity symbol is M
𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 (𝑖𝑛 𝑚𝑜𝑙𝑒𝑠) 𝑛
• 𝑚𝑜𝑙𝑎𝑟𝑖𝑡𝑦 = =
𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝑖𝑛 𝐿) 𝑉
○ Volume of a solution is affected by temperature; molarity may change if temper
§ So mixing two 50 mL solutions may not result in a 100 mL solution
• When the number of moles of solute do not change during dilution, the molarity of the
calculated as:
𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 (𝑚𝑜𝑙𝑒𝑠)
○ 𝑚𝑜𝑙𝑎𝑟𝑖𝑡𝑦 =
𝑡𝑜𝑡𝑎𝑙 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑟𝑒𝑠𝑢𝑙𝑡𝑖𝑛𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝑖𝑛 𝐿)
○ M1V1 = M2V2
§ Expresses that the amount of solute before and after the dilution with a so
Density
• Expressed in g/mL
• Always refers to the entire solution rather than just 1 of its components
Ex. Consider an aqueous solution that contains 70% HNO3 by mass and has a density of 1.42
of this solution?
, Reaction Types
September 11, 2022 8:05 PM
Acid-base reactions
1. Bronsted-Lowry theory
a. An acid is a molecule that can donate a proton (H+) to another substance
b. A base is a molecule that can accept a proton (H+) from another substance
2. Lewis theory
a. An acid is a species that accepts an electron pair
b. A base is a species that donates an electron pair
• Strong acids and bases are completely ionized in a solution
○ HCl is a strong acid since there are no HCl molecules in the solution
§ Only H+ and Cl- ions
• pH is the negative logarithm of the H+ concentration
○ Measured in moles per litre
• Changing the pH by 1 unit changes the concentration of H+ by a factor of 10
Salts
• A strong acid and a strong base forms a salt and water
• Acid + base --> salt + water
pH = -log10[H+]
[H+] = [H3O+] = 10-pH
pOH = -log10[OH-]
[OH-] = 10-pOH
pH + pOH = 14
Ex. What is the pH of a solution of 0.325 M H2SO4?
Ex. Find the pH of the solution resulting from the reaction of 250 mL of 0.350 M H2SO4 with 3
September 11, 2022 2:57 PM
• Isotopic abundance: % by number of each of the isotopes of an element
• Mass defect: the difference between the combined masses of protons and neutrons an
the nucleus
○ Normally the atomic mass of an isotope has a fractional value close to the mass
§ C-12 is the only exception because its atomic mass is equal to exactly 12u
○ The mass defect and non-integer masses of protons and neutrons are why all iso
C-12 have irregular atomic masses
Moles:
• Mole: number of atoms in exactly 12 grams of pure C-12
○ This is Avogadro's number, NA, which is 6.02 x 1023 mol-1
• Number of particles (atoms/molecules/ions) = number of moles x NA
• 1 ATOM of carbon-12 has a mass of 12 u
• 1 MOLE of carbon-12 has a mass of 12g
• Molar mass is now MM, not just M
○ Molar mass and molecular mass have the same value but different units
§ Molecular mass is in AMU (u)
§ Molar mass is in g/mol
!"#$%& ()#(*%+ () , +-%./%+
• Mole fraction:
0(01* !"#$%& () #(*%+
○ To make it a percent just x100
Ex. Determine the mole fraction and the mole percent of NaCl and NaNO3 in a mixture of 0.2
NaCl and 0.3564 moles of NaNO3
Ex. Determine the mole fraction and mole percent of carbon in glucose (C6H12O6)
(34567 8 9 345:; 3:77 8) = (34567 > 9 345:; 3:77 >)
• Average molar mass of a mixture: MM =
0(01* #(*%+
Ex. A sample contains 0.187 mol of NaCl, 0.850 mol of CaCl2, and 1.250 mol of SiO2. Find the
mass of this mixture
,Solutions
September 11, 2022 7:33 PM
Molarity
• The number of moles of solute in 1L of the solution
• Molarity symbol is M
𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 (𝑖𝑛 𝑚𝑜𝑙𝑒𝑠) 𝑛
• 𝑚𝑜𝑙𝑎𝑟𝑖𝑡𝑦 = =
𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝑖𝑛 𝐿) 𝑉
○ Volume of a solution is affected by temperature; molarity may change if temper
§ So mixing two 50 mL solutions may not result in a 100 mL solution
• When the number of moles of solute do not change during dilution, the molarity of the
calculated as:
𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 (𝑚𝑜𝑙𝑒𝑠)
○ 𝑚𝑜𝑙𝑎𝑟𝑖𝑡𝑦 =
𝑡𝑜𝑡𝑎𝑙 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑟𝑒𝑠𝑢𝑙𝑡𝑖𝑛𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝑖𝑛 𝐿)
○ M1V1 = M2V2
§ Expresses that the amount of solute before and after the dilution with a so
Density
• Expressed in g/mL
• Always refers to the entire solution rather than just 1 of its components
Ex. Consider an aqueous solution that contains 70% HNO3 by mass and has a density of 1.42
of this solution?
, Reaction Types
September 11, 2022 8:05 PM
Acid-base reactions
1. Bronsted-Lowry theory
a. An acid is a molecule that can donate a proton (H+) to another substance
b. A base is a molecule that can accept a proton (H+) from another substance
2. Lewis theory
a. An acid is a species that accepts an electron pair
b. A base is a species that donates an electron pair
• Strong acids and bases are completely ionized in a solution
○ HCl is a strong acid since there are no HCl molecules in the solution
§ Only H+ and Cl- ions
• pH is the negative logarithm of the H+ concentration
○ Measured in moles per litre
• Changing the pH by 1 unit changes the concentration of H+ by a factor of 10
Salts
• A strong acid and a strong base forms a salt and water
• Acid + base --> salt + water
pH = -log10[H+]
[H+] = [H3O+] = 10-pH
pOH = -log10[OH-]
[OH-] = 10-pOH
pH + pOH = 14
Ex. What is the pH of a solution of 0.325 M H2SO4?
Ex. Find the pH of the solution resulting from the reaction of 250 mL of 0.350 M H2SO4 with 3
