Semester 2 Final Review Part 1 Flashcards
What is a chemical reaction?
Process by which one or more substance change into one or more new substances
What are reactants?
Original substances in a reaction (written on left side)
What are products?
Substances that are created (written on right)
What is a chemical equation?
Equation that shows the chemical formulas and relative amounts of all reactants and products
What are signs of a chemical reaction?
Odor, color change, change in temp, formation of gas, precipitate
What is a chemical change?
New substance forms with properties that are different from the original substance
What are some chemical changes?
Density, boiling point, melting point
What is a physical change?
Changes of state which are not chemical changes
What are some physical changes?
Evaporation, condensation, melting, freezing
If energy is being released in a chemical reaction than it is a ?
Product
If energy is being absorbed in a chemical reaction than it is a ?
Reactant
What is a coefficient?
A number in front of the element or compound that multiplies the number of atoms
What happens if you cannot balance the equation do to half odd numbers?
Multiply current coefficients by 2
What are the five reaction types?
Combustion, synthesis, decomposition, single replacement, and double replacement
Why is classifying reactions important?
Allows scientists to predict products of reactions
What happens in a combustion reaction?
Carbon molecule reacts with oxygen and products are ALWAYS carbon dioxide and water
Heat is given off
What happens in a synthesis reaction?
Two atoms or compounds are being combined to form one compound
What happens in a decomposition reaction?
One compound breaks down into two smaller elements or compounds
Metal oxides and water make what?
Metal hydroxide
Carbonates break down into what?
Metal oxide and carbon dioxide
What happens in a single replacement reaction?
Single element reacts with compound and displaces another element from compound
What happens in a double replacement reaction?
Two compounds in an aqueous solution appear to exchange ions to form new compounds
What must one of the products be in a double replacement reaction?
One of the products must be a solid precipitate, a agase, or molecular compound such as water
Metal oxides and carbon dioxide form?
Carbonates
Metal hydroxides break into?
Metal oxide and water
Carbonates break down into?
Metal oxide and carbon dioxide
How do you know if an element will displace another element?
Use the activity series
How do you use the activity series?
If an element is listed above another element it can displace anything below it
What are the diatomic elements?
Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, and Iodine
Never found as single atoms
What happens to ionic compounds when they dissolve in water?
They separate into ions
When does a double replacement reaction take place?
If the dissolved ions react to form a precipitate, gas, or liquid
What are subscripts?
Numbers that tell you the number of atoms of that element
How can you predict if a precipitate will form?
Use the Solubility Rules
What are the solubility rules?
Guidelines that you use to determine if an ionic compound is soluble or insoluble
What does soluble mean?
Dissolves in water
What does insoluble mean?
Does not dissolve in water
What happens if a reaction forms an insoluble ionic compound?
Precipitate forms, indicated by (s)
What do total ionic equations show?
Show all the soluble ions and insoluble solid, liquid, or gases in compounds
What do net ionic equations show?
Only the ions that change in a reaction
What happens if there is no change?
No reaction occurs (solid, liquid, or gas must be formed in order to change)
What are spectator ions?
Ions that remain unchanged in the reaction
If one of the compounds is not soluble will the reaction take place?
Yes
If both of the compounds are soluble will the reaction take place?
No reaction occurs
What is a word equation?
A chemical reaction is expressed in words rather than chemical formulas
What is stoichiometry?
Branch of chemistry that deals with quantities of substances in chemical reactions
Can the amount of product be predicted based on your reactants using stoichiometry?
Yes
Can you calculate the amount of reactants needed to make the desired amount of product?
Yes
Can the amount of by-product be predicted?
Yes
What do stoichiometry problems begin with?
A balanced chemical equation
What do coefficients in a balanced chemical equation show?
Relative number of moles of a substance in the reaction
What are coefficients used to determine?
The mole ratios
What are mole ratios?
Conversion factors used to convert moles of one substance into moles of another substance
How do you solve a stoichiometry?
Set up mole ratio to cancel out substance that you are given and convert to substance that you want
How do you get from mass to moles?
Use molar mass
How do you get from volume to moles?
Volume (density) to moles
22.4 L in one mol
What is Avogadro’s number?
6.02 x 1023 particles/mol)
What is a limiting reactant?
A substance that controls how much product can form and is used completely in the reaction
What is a excess reactant?
Not completely used up in the reaction, leftover when reaction is complete
What is the theoretical yield?
The maximum product that can be made, always based on the limiting reactant
How do you find limiting and excess reactant?
Determine how much can be made from either substance, compare their amount of products, theoretical yield is lower amount of product
What is actual yield?
How much product is actually produced by the reaction, always less than theoretical yield
What is a percent yield?
Convenient way to describe the efficiency of reaction
What is the percent yield equation?
(Actual yield/theoretical yield) x 100
What is energy?
Ability to do work or produce heat
What two basic forms does energy exist in?
Potential and kinetic energy
What is potential energy?
Energy due to the composition or position of an object
What is kinetic energy?
Energy of motion
What type of energy do chemical systems contain?
Both kinetic and potential energy
What is the kinetic energy of a substance related to?
The constant random motion of its representative particle and proportional to the temperature
What does the potential energy of a substance depend on?
The type of atoms, the number and type of chemical bonds, and how the atoms are arranged
What is heat?
Energy that is in the process of flowing from a warmer object to a cooler object
What symbol is used to represent heat?
Q
What is a calorie (cal)?
The amount of energy required to raise the temperature of 1 gram of pure water by 1 degree Celsius
What nutritional Calorie equals how many calories?
1000 calories or 1 kilocalorie
What is a joule?
SI unit of heat and energy equivalent to 0.2390 calories
What does the total energy of a sample include?
Total energy of particles in a sample plus system’s volume times pressure
What is the symbol for enthalpy?
H
What happens as energy transfers away from a sample?
Particles kinetic energy slows down (decrease in temp)
What does enthalpy equal if the system is at constant pressure?
The heat transferred
What is temperature?
Measure of average kinetic energy of the particle in a sample of matter
What is molar heat capacity?
Energy needed to increase the temperature of 1 mol of substance by 1 K
What is the symbol and unit for molar heat capacity?
C and J/k mol
What is the molar heat capacity equation?
Q= nCΔt
What can molar heat capacity be used to calculate?
Heat absorbed and released
How are molar heat capacity and specific heat capacity related?
Molar mass
What can you use to find molar mass?
M x Cp = C
What is thermochemistry?
Branch concerned with the energy (heat) changes that accompany chemical and phase changes
What does thermochemistry help predict?
Whether a chemical reaction will occur and what kind of energy change it will have
What is a system?
Specific part of the universe that contains the reaction or process
What are the surroundings?
Everything else other than the system
What is the universe defined as in thermochemistry?
System + the surroundings
What is enthalpy?
The heat content of a system at constant pressure
How can you find enthalpy?
H = internal energy + (pressure x volume)
What is the symbol used for enthalpy?
H
What is the only way to measure the energy of a system?
A change in energy which is called molar enthalpy change
What would you use if you are looking for specific heat but you are only given mass and temperatures of both substances?
-mCpΔt= mCpΔt
Positive enthalpy changes are _____?
Endothermic
Negative enthalpy changes are ____?
Exothermic
What is 1 Calorie equal to?
4.1858 kJ
What is 1 joule equal to?
0.2390 calories
What are 1000 calories equal to?
1 Calorie
What is a calorimeter?
Insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process
What does a calorimeter determine?
Specific heat of an unknown metal
What is a thermochemical equation?
Balanced chemical equation that includes the physical states of all reactants and products and energy change
What is the energy change usually expressed as?
ΔH
What is the enthalpy of combustion?
ΔHcomb enthalpy change for complete burning of substance
What is the molar enthalpy of vaporization?
ΔHvap heat required to vaporize one mole of a liquid
What is the molar enthalpy of fusion?
ΔHfus is the heat required to melt one mole of a solid
If ΔH is negative
energy is released to the surroundings.
If ΔH is positive
energy is absorbed from the surroundings.
What is calorimetry?
Used to measure energy released or absorbed from a reaction by measuring a change in temperature of a standard liquid and setting enthalpy equal to the reaction change
ΔH lost = ΔH gained
What can be used to measure calorimetry?
-mCpΔt= mCpΔt
What is Hess’s Law?
If you add 2 or more thermochemical equations to produce a final equation, the sum of enthalpy changes is the enthalpy change for the final reaction
Why is the overall enthalpy change equal to the sum of the enthalpy changes?
If 2 processes start and end with the same reactants and products, they will have the same enthalpy change, even if the steps are different.
How can you use Hess’s Law?
Look for products and reactants for the desired equation, manipulate equations to put products and reactants in the correct locations, make sure whatever you do to the equation you do to ΔH
What equation is used to determine how the standard enthalpies of formation to determine the enthalpy change in a chemical reaction
ΔHrxn = ΔHproducts - ΔHreactants
What do you do when a coefficient is in front of the substance in the ΔHrxn = ΔHproducts - ΔHreactants
equation.
Multiply the ΔH by the coefficient when determining ΔHrxn
What is the standard enthalpy of formation?
The change in enthalpy that accompanies the formation of one mole of the compound in its standard state from its elements in their standard states. ΔHf
What is entropy?
A measure of the number of possible ways that the energy of a system can be distributed, units J/k
What is entropy related to?
Related to the freedom of the system’s particles to move and the ways they can be arranged
Is it true that all systems naturally become more random?
Yes
What are factors that increase entropy?
Particles’ freedom of movement increase, dissolving a solid, increase volume, increase energy, reducing the pressure of a gas
When does entropy increase?
As a substance changes from a solid to a liquid and from a liquid to a gas
If the reaction or process is exothermic, what happens to ΔSsurroundings?
Increase of temperature of surroundings occurs and ΔSsurroundings is positive
Is it true that elements can have values for S not equal to O
Yes
Reactions are more likely to occur when?
If enthalpy is negative (exothermic reactions), but some still occur if enthalpy is positive
A process is more likely to occur if entropy increases because?
It is becoming more random
What is free energy?
Energy that is available or leftover
What is it called for the reactions that take place at constant pressure and temperature with free energy?
Gibbs Free Energy
What is the Gibbs Free Energy Equation?
ΔGsystem = ΔHsystem – TΔSsystem
What does the tendency of a reaction to occur depend on?
Both ΔH and ΔS.
What is something to note when doing Gibbs Free Energy?
ΔS is given in J/K so it must be put into kJ in order to add or subtract to find ΔG
What is a spontaneous reaction?
One that, once begun, occurs with no outside assistance (means that reaction is possible)
What a reaction is spontaneous what is ΔG?
Negative
If ΔG is positive what will happen to the reaction?
Will not occur
If ΔG is 0 what will happen to the reaction?
System is at equilibrium
A more negative ΔG tends to occur in reactions that?
Release a lot of energy
ΔG depends on?
Temperature
A chemical reaction has NOT occurred if the products have?
The same chemical properties as the reactants.
An insoluble solid produced by a chemical reaction in a solution is called?
A precipitate
A solid produced by a chemical reaction that then separates from the solution is called a(n)…?
Precipitate
A _____ is a substance that speeds up a chemical reaction but does not participate in the reaction. It is written over the arrow in a chemical equation.
catalyst
Chemical equations are balanced so they do not violate the ___________.
law of conservation of mass
Nonmetal oxides react with water to produce ____________.
Acids
Enthalpy is?
Energy of a system at constant pressure.
How is a celsius temperature converted to kelvins?
By adding 273.15
The greater the kinetic energy of the particles in a sample of matter
The higher the temperature is.
In the expression q=nCΔT, what do q and n represent?
Heat and moles of particles
Compared with a single gas, a mixture of gasses is
More disordered
