Stoichiometry Flashcards
Stoichiometry
2mol C8 H18: 25mol 02
Ratio
The study of the numerical relationship between chemical quantities In a chemical reaction
Reaction stoichiometry
What do the coefficients in a chemical reaction specify
1CH8 —> 1 mole of CH8
The coefficients in a chemical reaction specify the relative amounts in loses of each of the substance involved in the reactions
What is a limiting reactant?
Least amount of product aka the limiting reagent
This will run out first
What is a theoretical yield?
Amount of product that can be made in a chemical reaction based on the amount of limiting reactant
How many you can get based on the limiting reactant
The actual amount of product made in a chemical reaction
(Assume that while making pizzas we burn a pizza, drop one on the floor, or other uncontrollable events happen so that we make only 2 pizzas)
Actual yield
We can determine the efficiency of making pizzas by calculating the percentage of the maximum number of pizzas we actually make.
In chemical reactions we call this the_____
Percent yield
actual yield ( 2 pizzas)/ 3 pizzas ( theoretical yield) x 100 = % yield
Reactants not completely consumed are called
Excess reactants
Calculating the limiting reactant
20-23
Calculating limiting reactant, theoretical yield, and percent yield from reactant masses:
What unit do we normally measure reactant quantities in?
To find limiting reactant and theoretical yield, we must first convert____ to____
Grams
Grams to moles
Solution concentration and solution stoichiometry:
What is solvent?
What is solute
A solution in which water is the solvent____
The majority of the solution
The minority component
Aqueous solution
To describe solutions accurately we quantify the amount of solute relative to solvent or
Concentration of solution
Two different descriptions of solutions match them
Solutions that have a small amount of solute compared to solvents
Solutions have a large amount of solute compared to solvents
Dilute solutions
Concentrated
A common way to express solution concentration is (molarity) (M)
Molarity is the amount of solute ( in moles)
Divided by the volume of solution ( in liters)
M= amount of solute (in mol)/ volume of solution (in L)
Solution Dilution:
Solutions are stored as concentrated___
Stock solutions
How do you make solutions of lower concentrations to stock solutions
More solvent is added
( the amount of solute doesn’t change, just the volume of solution)
Moles solution in solution 1 = moles solute in solution 2
The concentrations and volumes of the stock and new solutions are inversely proportional
M1x V1= M2 x V2
Molarity relates the ______ of a solute to the _____ of the solution
It can be used to convert between amount of ______ or _____ in a chemical solution
( the general conceptual plan for these kinds of calculations begins with the volume of a reactant or product
Moles
Liters
Reactants
Products
What happens when a solute dissolves?
There are_____forces between the _____ solute particles holding them together
There are also attractive forces between the ______molecules
Attractive
Solute
Solvent
When we mix the solute with solvent what happens
There are attractive forces between the solute particles and the solvent molecules
What will happen if there is a strong attraction between a solute and solvent?
If strong enough the solute will dissolve
Charge Distribution in a water molecule:
There is an ______ distribution of electrons within a water molecule which causes the oxygen side of the molecule to have a ________ charge and the hydrogen side to have a partial _______ charge
Uneven
Partial negative
Positive
Solute and Solvent interactions in a sodium chloride solution:
When a sodium chloride is put into water, the attraction of Na+ and Cl- ions to water molecules competes with the attraction among the oppositely charged ions themselves. Describe what that would look like.
Na+ Cl-
The partial negative of the O would attract with the Na+ and the partial positives of the H would attract to the Cl- ( Solvent- Solute interactions)
And the Na+ would attract with the Cl- ( solute- solute interactions)
Dissolution of Ionic compounds:
Summary- each ion is attracted to the surrounding water molecules and pulled off and away from the crystal.
When it enters the solution the ion is surrounded by water molecules insulating it from other ions. But what is the final result?
The result is a solution with free moving charged particleS able to conduct electricity
Like ants swarming around a piece of food they carry part of the lattice crystal apart
Electrolyte and Nonelectrolyte solutions:
what is formed when materials dissolve in water to form a solution containing ions ?
They will conduct electricity ( electrolytes)
What happens when a material that dissolve in water to form a solution with no ions
They wont conduct electricity ( nonelectrolytes)
Sugar in a solution vs salt in a solution
Ionic substances such as NaCl that completely dissociate into ions when they dissolve in water are called
Strong electrolytes
Except for acids, most molecular compounds exp sugar dissolve in water as intact molecules or
Non electrolytes
Acids ionize to varying degrees in water. Those that completely ionize are ________ acids and those that don’t are _______ acids
Strong
Weak
Acids are molecular compounds that ______ when they dissolve in water
When acids _____ they form____ cations and also anions
Ionize x2
H+
The percentage of molecules that ionize varies from one acid to another
Acids that ionize virtually 100% are called
Acids that ionize only a small percentage are called _____
Strong acids
Weak acids
Recap of Strong and Weak electrolytes:
Strong electrolytes?
Materials that dissolve completely as ions
- ionic compounds are strong acids
- solutions are good conductors of electricity
Weak electrolytes?
Are materials that dissolve mostly as molecules but partially as ions
- weak acids
Solutions conduct electricity but not well
When ionic compounds dissolve in water, the anions and cations are serperated from each other what is this called?
Na2S(aq)——>
When polyatomic ions dissociate, the polyatomic group stays together as one
Na2SO4 (aq)—-> 2Na + (aq) + SO4^2- (aq)
When strong acids dissolve in water the molecule Ionizes into H+ anions
H2SO4 (aq) —-> 2H+(aq)+ SO4^2- (aq)
Dissociation
—> 2Na+ (aq) + S2- (aq)
What makes a compound soluable?
What makes a compound insoluble?
Not all ionic compounds dissolve in water exp AgCl
When an ionic compound dissolves in water it does not stay intact but its __
Dissolves in water (soluable)
Does not dissolve in water (insoluable)
AgCl in water remains a solid and appears as a white powered at the bottom of the water
Component element ions dissolved in water
Empirical method
Guidelines
Test the experiments
Then develop some rules based on those experimental results
Review slide 50
Okay
Reactions in which a solid forms when we mix 2 solutions
- reactions between aqueous solutions of ionic compounds produce an ionic compound that is______
Precipitation
Insoluble in water ( precipitate)
No precipitation means
No reaction
Predicting precipitation reactions:
1 determine what ions each aqueous has
2) determine the formulas of possible products
-exchange ions (+) ion from one reactant with (-) ion from another
- balance charges of combined ions to get the formula of each
product
3)
3) determine solubility of each product in water
- use the solubility rules
- if the product is insoluble or slightly soluble it will ppt
4) if neither product will ppt write no reaction after the arrow
Continued:
5) if product is insoluble write (s) after it to signify a solid
6) if product is soluble write (aq) after the formula to indicate the aqueous
6) balance the equation
- remember to change only coefficients not subscripts
Representing aqueous reactions:
What is a molecular equation?
An equation that is written as if all the substances were molecular, even though some substances may exist as ions
What is a complete ionic equation?
An equation that has substances which exist as ions in ionic form
H+ (aq) Na+(aq) +Cl- (aq) + OH- (aq) ——> Na+ (aq) + Cl- (aq) + H20
Rules for writing a complete ionic equation:
(Aq) strong electrolytes ( soluble salts, strong acids, strong bases) are written as ions
Insoluble substances, weak electrolytes, and non-electrolytes are written in molecule form
-solids, liquids, and gases are not dissolved, hence molecule form
Spectator ions
Pb2+(aq) + 2NO3-(aq) + 2K+ (aq) + 2Cl-(aq)—->
PbCl2(s) + 2K+ (aq) + 2NO3-(aq)
Spectator ions don’t participate in the reaction (soluble salts, strong acids, and strong bases)
In the complete ionic equation, some of the ions in solution appear unchanged on both sides of the equation
Net ionic equation
When all the spectator ions are removed from the equations
Acid- Base and Gas- evolution reactions:
They’re 2 important reactions
Now what is an acid base reaction? And what is another name for it?
Acid reacts with a base and the 2 neutralize each other producing water or weak electrolytes
Another name for A-B reactions is Neutralization reactions
What happens in a gas- evolution reaction?
Gas is produced resulting in bubbling
Bubbling is a cause because its less dense
How do acid- base and
gas- evolutions occur?
Many G-E reactions are also A-B reactions
Because like ppt reactions
It occurs when an anion from one reactant combines with a cation of another
What is an Arrhenius Definition:
Acid what is it?
What does acid to in a solution? (H30+)
Substance that produces H+ on (aq) solutions
the H+ that it produces bonds with water to produce hydronium ion
What is a poly protic acid? And what do they do?
An acid that contains more than 1 ionizable proton and release them sequentially
(Polyprotic acid)
Is there a difference in the ionizable proton after releasing them in sequential order?
Yes the first ionizable proton is strong while the subsequent ionizable protons are weak
What is a base?
A substance that produces OH- ions in aqueous solution
