Chemical Reactions
How do you balance chemical reactions?
Identifying the coefficients, multiply the coefficients on both sides (reactants and products) until you have the same amount of each element (or polyatomic ion) in both sides of the reaction
What is a precipitate?
An insoluble ionic solid produced in a reaction.
If you have grams of a compound, and you need to find atoms, how would you do it?
Grams / molar mass * avogadro's number
What are the units for energy?
Joules or kilojoules (0.001 joules)
How can you convert calories to joules?
1 calorie = 4.184 Joules
What type of reaction is this?
4Fe + 3O2 --> 2Fe2O3
Synthesis!
A + B --> AB
If you're given a reaction, like
AgNO3(aq) + NaCl(aq) --> AgCl(s) + NaNO3(aq)
how do you find the net ionic reaction?
First find the ionic reaction, so split the reactants and products into ions, for example AgNO3 becomes Ag+ + NO3-. Remember that solids are not split into ions. Then, cancel out whatever repeats on both sides of the reaction.
What is a limiting reactant?
The compound that will run out first in a reaction.
Define the terms: potential energy, kinetic energy, thermal energy
potential: energy possessed by an object by virtue of its position
kinetic: energy that results from motion
thermal: kinetic energy associated with random motion of atoms and molecules
When is W positive or negative?
Work done ON the system W = +
Work done BY the system W = -
List at least 3 of the 6 types of reactions
Combination, decomposition, single replacement, double displacement, combustion, acid-base neutralization
How can you identify an acid-base/neutralization reaction?
The reactants are an acid and a base, and the product is a salt and water.
You are given a problem of a compound with concentration, and a volume. How can you find the mass?
First find moles using the molarity formula.
moles = M * L
Then use the molar mass to convert it to grams.
grams = moles * molar mass
Explain the formula
q = mcΔT
Q = heat
M = mass
C = specific heat capacity
ΔT = change in temperature
What is the specific heat capacity of water?
4.184 J/g*C
How can you identify a solvent from a solute?
A solvent is present in a larger amount in the solution, while the solute is present in a smaller amount.
What are the reactants and products of a combustion reaction?
hydrocarbon + oxygen --> co2 + water
If you have a compound like SOCl2, how would you find the molar mass?
Looking at the periodic table, adding the molar masses for each element making up the compound. (S+O+Cl+Cl=118.97 g/mol)
What is Hess's law?
When we manipulate two or more reactions and their enthalpy changes in order to find another reaction's ΔH value.
What is calorimetry?
The study of heat transfers by measuring the ΔT in the substances involved.
What is an electrolyte?
A substance that dissolves in water to yield solution that conducts electricity.
Check table 4.1 to remember the 7 strong acids, which are strong electrolytes. (HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4)
How can you know the oxidation states?
What is a titrant and how can you find the volume used?
The solution added during a titration.
Final volume - initial volume
What is the standard state of a substance?
The state in which the substance is most stable at 25ºC and 1 atm pressure.
How do you find the standard enthalpy of reaction (ΔHºrxn)?
∆Hºrxn = ∑m*∆Hºf(products) – ∑m*∆Hºf(reactants)