CHEM121 Study Guide Test 3
Ch 7
definitions of stoichiometric ratio, limiting reactant, mass conservation, percent yield
[𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝑜𝑓 𝐵] 𝑚𝑜𝑙𝑒𝑠 𝐵 𝑑𝑒𝑠𝑖𝑟𝑒𝑑
be able to write a stoichiometric ratio [𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝑜𝑓 𝐴] 𝑚𝑜𝑙𝑒𝑠 𝐴 𝑔𝑖𝑣𝑒𝑛
Mole-Mole conversions
convert moles of one compound to moles of another in the same reaction
Mole-Mass conversions
convert moles of one compound to mass of another in the same reaction
Mass-Mass conversions
convert mass of one compound to mass of another in the same reaction
Determine limiting reactant from amounts of two or more reactants
Calculate theoretical yield from limiting reactant
Calculate % yield from moles of reactant and actual yield
use moles reactant to find theoretical yield; % yield = (actual yield/theor yield)*100%
Ch 8
Definition of solution, solute, solvent
Definition of solubility and be able to identify an insoluble salt
know and use solubility rules from our reference (provided on test)
Molarity and associated calculations
Calculate the molarity of a solution given mass or moles of solute and volume 𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦 =
𝑚𝑜𝑙𝑒𝑠 𝑠𝑜𝑙𝑢𝑡𝑒
𝑙𝑖𝑡𝑒𝑟𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛
Calculate moles or volume from molarity
Perform dilution calculations using 𝑀𝑠 𝑉𝑠 = 𝑀𝑤 𝑉𝑤 (where s and w represent the strock and dilute solutions)
Identify type of chemical reaction from full reaction
precipitation, neutralization, redox
Identify Reduction-Oxidation
Determine Oxidation Numbers and write a half reaction for a redox reaction
Identify: substance reduced, substance oxidized, reducing agent, oxidizing agent
Write molecular, ionic and net ionic equations for a chemical reaction
Predict products of a reaction (from just reactants)
for any double replacement reaction of two ionic compounds (precipitation, neutralization)
Solution Stoichiometry
Calculate moles from M and V (molessoln = M x V(in L))
Calculate M from mass of solute and V (molespure = mass/MM, then M= moles/VLiters)
Given the volume and molarity of a solution, find the amount (mass, moles or molarity) of another substance it
reacts with or produces
Given the mass of a reactant or product, find the volume or Molarity of another substance it reacts with or
produces
Ch 9
Describe different forms of energy and identify units of energy
Recognize an energy measurement by its units (Joules, J, kJ, cal, kcal)
Know the law of conservation of energy [E not created nor destroyed]
Total internal energy change E= q + w = heat absorbed + work done to system
Be able to determine the direction of energy flow
Endothermic (and Endergonic) mean that the surroundings are transferring heat (or energy) to the system (+)
raising temperature, melting, boiling, breaking bonds, or removing electrons are all endo processes
Exothermic (and Exergonic) mean that the system is transferring heat (or energy) to the surroundings (-)
lowering temperature, freezing, condensing, making bonds, or moving electrons to lower orbitals are all exo
Use specific heat to calculate heat loss or gain, temperature change, or mass of a sample.
Know Δ (delta) refers to a change in a property [find by subtracting value before from value after]
ΔT = rise in temperature = Tf – Ti if a substance is cooling, it is negative
Calculate heat absorbed (q) when a sample changes temp but not state (q=mass * specific heat *T)
Calculate mass or specific heat of a sample from heat absorbed/released (q) and temp change (ΔT) (rearrange
q=mass * specific heat *T)
Calculate energy absorbed from reacting a specific number of moles of reactant from the reaction enthalpy
q = n*(ΔHrxn/coefficient of reactant)
Calculate a property in calorimetry experiments
-qsystem = qsurroundings if there are multiple surroundings objects, add q of each on surroundings side
the surroundings (calorimeter, solution/water etc) change temperature so use q = m Cs ΔT
the system can be changing temperature or changing state or undergoing a chemical reaction; use the
appropriate q equation for whichever process it is
Calculate enthalpy of reaction from standard enthalpy of formation
Enthalpy of reaction = sum of (n*ΔHfo )products - sum of (n*ΔHfo )reactants
Know ΔHfo of a standard state element (monatomic or diatomic form, in natural state at room temperature) is 0
Calculate enthalpy of reaction from bond energies
Enthalpy of reaction = sum of (qty * bond energies)BROKEN in reactants - sum of (qty*bond energies)MADE in products
Ch 10
Describe solids, liquids, and gases at the level of bulk material and at the level of the particle.
Define pressure and the units involved.
Pressure = Force / Area
Convert pressure units (equalities of units will be given)
Be able to read the pressure of a gas from a manometer picture
Understand and apply the gas laws involving pressure, volume, temperature
Know Boyle’s Law: it’s an inverse relationship (P  then V ) 𝑃1 𝑉1 = 𝑃2 𝑉2
𝑉1
𝑉
Know Charles’ Law: it’s a direct relationship (V  then T )
= 𝑇2
𝑇
1
Know Guy-Lussac’s Law: it’s a direct relationship (P  then T )
Know Combined Gas Law:
𝑃1 𝑉1
𝑃 𝑉
= 2𝑇 2
𝑇1
2
2
𝑃1
𝑃
= 2
𝑇1
𝑇2
Use the gas laws to determine trends (eg. if x , figure out if another variable  or )
Use the gas laws to solve for a gas property value
Be careful when solving for T2 that you get T to the top of fraction
Understand that T must always be in K
Use the ideal gas law to solve for P, V, T, or n of a gas when given three of the gas equation.
Know Ideal Gas Law: 𝑃𝑉 = 𝑛𝑅𝑇
Remember that for the ideal gas law, the units of P and V must match those of the R value used
Use partial pressures to calculate the total pressure of a mixture of gases.
Know Dalton’s Law
𝑃𝑡𝑜𝑡𝑎𝑙 = 𝑃1 + 𝑃2 + …
Know how to use Dalton’s law to correct for water vapor when collecting wet gases
Gas Stoichiometry
Calculate moles from P, V and T (molesgas = P(in atm) x V(in L)/(R x T(in K)) )
Calculate P, V or T from moles and the other two properties
Given the P, V, T of a gas reactant or product, determine how many moles are needed to react (or how many
moles can be produced) of another chemical in the chemical reaction