Unit 4 & 5: Solution Stoichiometry and Thermochemistry Flashcards
Definition of solution
A homogeneous mixture of two substances
What are the two parts of a solution?
- Solute
2. Solvent
Definition of solute
The substance which gets dissolved
Definition of solvent
The substance which does the dissolving
What is the solute usually like? (physical features)
- usually the smaller amount
- usually a solid (not always)
What is the solvent usually like? (physical features)
- larger amounts
- usually a liquid
Definition of concentration
The amount of solute dissolved in a given amount of solvent
“the greater amount of solute dissolved in a given amount of solvent; the greater the concentration”
Definition of molarity
what is its symbol
a way to quantify concentration in chemistry
symbol: M (capital)
What is the equation for molarity?
M= (moles of solute) / volume (L) of solution
Definition of dilution
Reducing the concentration of a chemical solution
What is the main method of diluting?
Adding water
How do you mix a solute into a solution?
Pour half of the solution into the beaker, then add the solute, then add the rest of the solution
Which is poured first, water or acid?
you pour acid into water…ALWAYS!
What is the equation that is used when you are trying to find the initial molarity, initial volume, final molarity, or the final volume?
M1(V1)=M2(V2)
Definition of acid and characteristics
any compound that is able to ionize and form a hydrogen ion (H+ ions) (Ex. HNO3, HC2H3O2,etc)
Characteristics: Sour taste
Definition of monoprotic acid
acid that yields one H+ per molecule of acid
Definition of diprotic acid
acids that yield two H+ per molecule of acid
Definition of bases and characteristics
any substance that is able to accept (react with) H+ ions
Characteristics: Bitter taste, slippery
What does bases produce when dissolved in water?
OH- ions, therefore, bases usually end with OH- (ex. LiOH, NaOH, etc)
Definition of Salt
Any ionic compound whose cation comes from a base and whose anion comes from an acid. (metal and nonmetal)
Definition of neutralization
a reaction where an acid and base are mixed to make a salt and water (harmless)
Definition of electrolyte
Solutes that exist as ions in a solution. Also conducts electricity
Definition of a non-electrolyte
the solutes do not separate into ions. Therefore, don’t conduct electricity
Are non-electrolytes still soluble even if they do not break into ions?
YES
Definition of strong electrolyte
any substance that exists NEARLY all as ions in a solution
most ionic compounds and good conductors
Definition of weak electrolyte
compounds that only PARTLY ionize in a solution. *soluble
*poor conductors
How does a strong acid or base act in water then?
completely ionize in water…good conductor
How does a weak acid or base act in water then?
only partially ionize in water…poor conductor
What are the rules to identify strong and weak electrolytes? (4 rules) (and for rule 2 and 3 what are the exceptions?)
- most salts ARE strong electrolytes
- most acids are weak electrolytes (except: HCl2, H2SO4, HNO3 HBr, HI, AND HClO4)
- Bases made with: Hydroxide (OH-) and either group 1 (alkali) or group 2 (alkaline earth) metals are STRONG…(except NH3)
- Most other substances are non-electrolytes
what is the conversion between grams, volume(or molarity), moles, and particles
Grams —-(use molar mass)—-> moles–(use avagadro’s #)–> Particles OR moles ——(use molarity(M))—> volume (or molarity)
Definition of titration
a method of determining the concentration of an unknown solution
What is needed for a titration?
- standard solution: a solution with a known concentration (M)
- unknown solution: the solution you are trying to determine the concentration of
Definition of equivalence point:
the point at which stoichiometrically equal amounts get together. (creates a neutral solution!)
What indicator did we use in class to get the equivalence point?
phenolphthalein (pink= base and clear = acid)
Definition of end point
when you are close to the equivalence point
Definition of oxidation numbers
in short, oxidation numbers are useful for identifying how many electronss have been taken away from an atom (creating a positive oxidation number) or how many have been gained by an atom (creating a negative oxidation number)
What are the 5 steps to writing net ionic equations
- first write the balanced molecular equation
- then ask yourself (for each molecule): a. is it soluble? (is it aqueous?) b. is it a STRONG electrolyte? (if the answer to either question is no, then it does not completely dissociate!!)
- write the complete ionic equation by separating the ions that have completely dissociated
- cross off the spectator ions in the complete ionic equation
- write the remaining ions and non-aqueous molecules
What is a molecular equation?
a balanced equation that shows the complete formulas of reactants and products and their states of matter. (need solubility charts)
What is a complete ionic equation?
a balanced equation that shows the aqueous reactant and products that are able to completely dissociate, break up into their separate ions. REMEMBER: only strong electrolytes will dissociate
What is a net ionic equation?
an equation that has had the spectator ions removed. it will only include the ions that are directly involved in forming the non-aqueous products
Definition of solubility
the maximum amount of solute that will dissolve in a certain amount of solvent (at a given temp and for solids and gases)
Definition of saturated solution:
a solution that is full with solute. the solvent has dissolved the maximum it can for that temp
Definition of unsaturated solution:
a solution that can accept more solute. the solvent has not yet dissolved all that it can
Definition of supersaturated solution:
a solution that has more solute dissolved than it normally should (only happens in specific conditions)
What are the 4 things solubility depends on?
- temp
- amount of solvent
- type of solvent
- The surface area of the solute
Definition of solubility curves:
a graph showing the solubility of a solute as temp changes
How does solubility change for solids?
as temp increases, solubility increases
How does solubility change for gases?
as temp increases, solubility deacreases
What is the first law of thermodynamics? (a.k.a law of conservation of energy)
energy is neither created or destroyed
What are the two parts of a chemical reaction?
- system
2. surroundings
What is a system in a chemical reaction?
usually the chemical reactions. What we single out for study
What are the surroundings of a chemical reaction?
everything around the reactions. Ex. the gases surrounding it, the container, the room, etc
What is a closed system?
when no mass is gained or lost
no exchange of matter occurs w/environment
BUT does exchange heat and work
Does energy start with low or high energy and go to low or high energy?
starts with high energy to low energy
Definition of internal energy
The total energy (E) of a system
-all of the potential energy (PE) and kinetic energy (KE)
What is potential energy
the energy possessed by a body by virtue of its position relative to others, stresses within itself, electric charge, and other factors.
What is kinetic energy?
energy that a body possesses by virtue of being in motion.
What is ΔE and what is its equation?
ΔE means the change in the internal energy of a chemical system. its equation is ΔE = E final - E initial
Definition of endothermic and how can you tell if the answer to a ΔE equation is endothermic?
When the system has gained energy from the surroundings. Heat coming in not out. and ΔE has to be a + value
Definition of exothermic and how can you tell if the answer to a ΔE equation is exothermic?
The system has lost energy to the surroundings (energy out!). ΔE has to be a - value
What is the equation for the first law of thermodynamics?
ΔE= q + w q= the heat added to or given off from the system w= the work done on or by the system *heat added to a system (+ value) *heat taken away (- value)
Definition of state function
a property of a system that is determined by the specifying of its condition or state
ex. temp, pressure, location, etc
* **only depends on the present condition NOT how it got there
What is internal energy (ΔE)
STATE FUNCTION
- The amount of energy within a system
- only depends on the initial and final states of the system, not on how change occurs
is work a state function?
NO
Definition of enthalpy
the amount of heat absorbed or released under constant pressure (change in heat)
symbol: ΔH = H final - H initial
What is equation for ΔH?
ΔH +
if the value of a ΔH equation is positive then what does this mean? what if the value is negative?
positive: endothermic
negative: exothermic
What is enthalpy of reaction also known as? what is its equation? And what does this determine?
- also know as heat of reaction
- ΔHrxn = Hproducts - Hreactants
- determines the heat or energy in a reaction or chemical equation
can enthalpy be used as a conversion factor?
YES
What is calorimetry?
the measurement of heat flow into or out of a system (ΔH)
Definition of calorimeter
Equipment used to measure calorimetry
Definition of heat capacity
The amount of heat needed to raise a substances temp by 1K or 1 degree Celsius
Fill this in:
The ____ the heat capacity of a substance, the ____ energy needed
___ mass or amount of a substance, ____ heat energy required
- Higher, more
2. more, more
Definition of molar heat capacity
the heat capacity of 1 mole or a substance
Definition of specific heat capacity (C)
The heat capacity for 1 g of a substance AKA specific heat
Equation for specific heat
C= amount of heat transferred (J) / mass in grams (g) * change in temp. (K or C)
or C = q / (m) * (ΔT)
amount of heat transferred for a substance can also be calculated with which equation?
q = m * c * ΔT
What is constant pressure calorimetry?
pressure is held constant which allows for direct measurement of ΔH
ΔH = Qp (which means heat transferred under constant pressure)
What is constant volume calorimetry?
substance tested undergoes complete combustion and reaction takes place in a sealed container filled with a set volume of water
Definition of thermodynamics
The study of energy (or heat) and its transformations (changes)
Definition of Force
a push or pull on an object
Definition of energy
the capacity to do work or transfer heat
Definition of work
the energy used to cause an object to move against a force
Definition of Heat
The energy used to cause the temp of an object to increase
Definition of temperature
the measurement of the average kinetic energy of the molecules in an object
What is the SI unit for energy?
Joule (J)
Definition of calorie (cal)
used to measure energy in a chemical reaction but not an SI unit used in chemistry
1000 cal = I Cal (food calorie) = I kcal
1 cal = 4. 184 ***
Definition of heat of formation (ΔHf)
The formation of a substance from its individual elements and the heat energy involved
Definition of a standard state
the most stable form of a substance at a given temp and pressure
*standard condition must exist so chemists can compare the ΔHf values (found on a table)
Standard Heat of Formation (ΔH°f)
the change in enthalpy for a reaction that forms 1 mol of a compound from its elements
UNITS FOR ΔH°f is KJ/ Mol
What is the ΔH°rxn equation?
ΔH°rxn = ΣnΔH°f (products) - ΣmΔH°f (reactants)
n and m = # of moles
Definition of Food value
the amount of energy released when 1 g of a substance is burned
what is the fuel value of carbohydrate, fat, and protein
carbohydrate: 17 kj/g
Fat: 38 kj/g
protein: 17 kj/g
