A Review of Moles
What is a Mole?
The mole is the amount of substance that contains as many particles as there are in exactly 12 grams of carbon-12.
The amount of substance that contains the Avogadro number of particles.
1 mol = 6.02 x 1023 particles
In terms of particles, Avogadro’s number represents 6.02 x 1023 parts of any item:
 Atom - Element
 Molecule
o Molecular compound (non- metals)
o diatomic (O2, N2, H2 etc.)
o polyatomic ions
 Formula unit
o Ionic Compounds (Metal and non-metal)
Mole-Particle Relationships
1. Converting moles to particles
Amount of moles x 6.02 x 1023 particles = particles unit given
1 mole given
2. Converting particles to moles
Given particles x
1 mole given
= moles given
6.02 x 1023 particles
Practice
1.
How many atoms are in 6.5 moles copper?
2. How many molecules are in 3.4 moles of carbon dioxide?
3. How many formula units are in 2.2 moles of sodium chloride?
4. Determine the number of moles in 5.7 x 1022 molecules hydrogen gas?
5. How many moles of water are in 7.5 x 1024 molecules water?
Molar Mass
The molar mass is defined as the mass of one mole of a pure substance. The molar mass is the sum of the average
atomic masses of all of the atoms in the molecule, formula unit, or ion.
 Units are grams/mole (or g/mol)
Mass-Mole Relationships
A Converting moles to mass
Amount of moles x molar mass (grams) = molar mass (grams)
1 mole given
B Converting mass to moles
Mass given x
1 mole given
= moles given
Molar mass given
Practice
1. How many grams are in 4.2 moles iron?
2. How many grams are in 1.5 moles of sodium carbonate?
3. What is the mass of 1.75 moles of hydrogen gas?
4. How many moles are 56.5 grams of sodium chloride?
5. How many moles are in 79 grams of glucose?
Molar Volume Relationships
The volume occupied by one more of any gas at STP. One mole of any gas at STP occupies 22.4 liters.
Standard temperature and pressure (STP)
 Standard temperature = 0C or 273 K
 Standard Pressure = 101.3 kPa or 1 atmosphere
1. Converting moles to volume
Amount of moles x
22.4 liters = volume (liters)
1 mole given
2. Converting volume to moles
Volume given (in liters) x
1 mole given
22.4 liters
= moles given
Practice
1. How many liters of gas are in 2.5 moles hydrogen gas at STP?
2. What is the volume of 5.1 moles of carbon dioxide gas at STP?
3. How many moles are in 8.5 liters of oxygen gas at STP?
4. How many moles are in 120 liters of nitrogen monoxide gas at STP?
5. How many molecules are in 76 grams of glucose?
6. What is the volume of 6.4 grams of oxygen gas at STP?
Stoichiometry
The calculations of quantities in chemical reactions based on a balanced equation. The mole ratio of one substance
to another using the coefficients in a balanced equation.
When you mix hydrogen gas (H2) and oxygen gas (O2) nothing much happens. But when you add a spark to the
mixture, all of the molecules combine and eventually form water (H 2O). Like this...
2H2 + O2 --> 2H2O
The coefficient indicate there are 2 moles of hydrogen and 1 mole of oxygen form 2 moles of water. The mole
ratio of hydrogen to water are:
2 mol H2
2 mol H2O
2 mol H2O
2 mol H2
Mole Ratio – Mole to Mole Conversions
4 NH3 (g) + 6 NO
1.
(g)
→ 5 N2 (g) + 6 H2O
(g)
What are the mole ratios of NO to H2O?
2. How many moles of water are produce from 8 moles of nitrogen monoxide?
3. What are the mole ratios of NH3 to N2?
4. How many moles of nitrogen gas are produced from 2 moles of ammonia (NH3)?
5. How many moles of ammonia (NH3) are required to produce 45 moles of nitrogen gas?
___ Mg
(s)
+ ___ HCl
(aq)
 ___ MgCl2
(aq)
+ ___ H2 (g)
6. How many moles of hydrogen are produced by 5.5 moles of hydrochloric acid?
7. How many moles of hydrochloric acid are required to produce 7.5 moles of magnesium chloride?
Mole - Mass Stoichiometry Problems
Given mass → given moles → wanted moles → unknown mass
There are four distinct steps to mole-mass stoichiometry problems:
 write a balanced equation
 change the starting quantity to moles
 apply the mole ratio from the equation
 convert the new moles to the requested units
4 NH3 (g) + 6 NO
(g)
→ 5 N2 (g) + 6 H2O
(g)
Moles to Mass
1. What is the mass of water produced from 4 moles of ammonia (NH3)?
2. What is the mass of nitrogen monoxide required to produce 25 grams of nitrogen gas?
Mass to Mole
3. How many moles of nitrogen gas are produced from 80 grams of ammonia gas (NH3)?
4. How many moles of ammonia are required to produce 40 grams of nitrogen gas?
Mass to Mass
5. How many grams of ammonia are required to produce 60 grams of water?
6. How many grams of nitrogen monoxide are required to produce 35 grams of nitrogen gas?
Unit 6—Gas Laws
BOYLE, CHARLES, GAY-LUSSAC, AND THE COMBINED GAS LAW
1.
A gas sample occupies 100 mL at 760 mm Hg.
What volume does the gas occupy at 400 mm Hg?
Define variables:
2. 4. Nitrogen gas in a steel cylinder is under a
pressure of 120 atm at 25°C. What will the
pressure in the tank be of the tank is left in the
sun and the internal temperature rises to 55°C?
Define variables:
Formula:
Show work:
Formula:
Show work:
Answer Question (Check work):
Answer Question (Check work):
3. An ideal gas occupies 350ml at 270 mm Hg and 65C. If the pressure is changed to 1.6 atm and the
temperature is increased to 100C, what is the new volume?
Define variables:
Formula:
Show work:
Answer Question (Check work):
4. A constant volume of oxygen is heated from 100C to 185C. The initial pressure is 3.2 atm. What is the final
pressure?
Define variables:
Formula:
Show work:
Answer Question (Check work):
5. A sample of 25L of NH3 gas at 10C is heated at
constant pressure until it fills a volume of 45L.
What is the new temperature in C?
Define variables:
Formula:
Show work:
Answer Question (Check work):
Ideal Gas Law
Universal Gas Constant (R)
PV = nRT
(1 𝑎𝑡𝑚)(22.4 𝐿)
𝑃𝑉
=
(1 𝑚𝑜𝑙𝑒)(273 𝐾)
𝑅𝑇
P = pressure
𝑅=
V = volume
𝑅 = 0.0821
𝑎𝑡𝑚 𝐿
𝑚𝑜𝑙 𝐾
n = moles
T = temperature
1. What is the volume at STP of a sample of CO2 that has a volume of 7.50 L at 30.0°C and 0.75 atm?
Define variables:
Formula:
Show work:
Answer Question (Check work):
2. A 75.0 mL container holds 62 moles of gas at a temperature of 215° C. What is the pressure in
atmospheres inside the container?
Define variables:
Formula:
Show work:
Answer Question (Check work):
3. What is the volume of a sample of O2 that has a mass of 50.0 g and is under a pressure of 1.20 atm at
27.0°C?
Define variables:
Formula:
Show work:
Gas Laws and Stoichiometry
_____ Mg + _____ HCl → _____ H2
1.
+
_____ MgCl2
If 20.2 grams of Mg react completely, how many liters of H2 gas are produced at STP?
2. If 57 ml of H2 gas is produced at STP, what volume of 6 M HCl reacted?
____ KClO3(s)  ______ KCl(s) + ______ O2(g).
3. Solid potassium chlorate (KClO3) decomposes to produce solid potassium chloride (KCl) and oxygen
gas (O2). What volume of oxygen gas, measured at 40.0°C and 650 mm Hg, will be produced when 13.5
g of potassium chlorate is decomposed?
Define variables:
Formula:
Show work:
Answer Question (Check work):
4. Solid iron(II) chloride (FeCl2) is decomposed to produce solid iron (Fe) and chlorine gas (Cl 2)
according to the balanced chemical equation: FeCl2(s)  Fe(s) + Cl2(g). What volume of chlorine gas,
measured at 71.7°C and 1.33 atm, will be produced when 98.4 g of iron(II) chloride is decomposed?
Define variables:
Formula:
Calculating Specific Heat
Q=mc T
1.

A 2.0 g sample of iron was heated from 0°C to 20.°C. It absorbed 17.6 J of energy as heat. What is
the specific heat of a piece of iron?
2.
How much energy does a copper sample absorb as heat if its specific heat is 0.384 J/g·°C, its mass is
4.00 g, and it is heated from 10.0°C to 40.0°C?
3. Find the specific heat of a material if a 3 g sample absorbs 25 J when it is heated from 30°C to 50°C.