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Chemistry > 2.2 (Stoichiometry) > Flashcards

2.2 (Stoichiometry) Flashcards

(62 cards)

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1
Q

Drop and swap method for ionic compounds

A

Swap the values, ditch the signs
X with +2 and Y with -3
It becomes
X3, Y2
If one is positive # and one is -# they cancel each other out
With polyatomic ions bonding protect the ion w parentheses when you do it

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2
Q

What always ends in ide?

A

Monatomic anions always end in ide

If anything else it’s prob a polyatomic ion

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3
Q

What is drop and swap shortcut for?

A

Balancing charges in an ionic compound

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4
Q

Ionic charge trends

A 
First group +1
 Ag +1
Second group, +2
Zn, Cd +2
Al, Ga, +3
N,P, -3
O, S, Se -2
F, Cl, Br, I -1
Noble gases 0
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5
Q

Grams to moles

A

molar mass-multiply each element’s atomic weight by how many atoms are present in the formula, then add the answers and add g/mol to the answer
Then use the proportion of g of substance/mol of substance = (molar mass of substance in g/1 mol)

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6
Q

Percent composition

A

Percentage of each element in a compound by mass
Mass of each element in g per mole
(Mass of element1 divided by mass of compound)100=percent of element 1
Subtract that from 100 in a binary compound to find the other one

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7
Q

Empirical Formula

A

Non reducible shows the smallest whole number mole ratio of the different atoms in the compound

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8
Q

Empirical formula-if same ratio but different molecular formulas, then what?

A

All diff compounds w diff sizes, they all have the same basic ratio if they have the same e formula

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9
Q

Molecular Formula

A

shows the actual number of atoms in the compound

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10
Q

Using Percent Composition to Determine Empirical Formula

A
  1. Change from mass percentages to mass in grams. (Assume you have 100 g of the compound.)
  2. Change from grams to moles for each element using molar mass!
  3. Divide the number of moles of each element by the smallest number in order to find the ratio of
    smallest whole number for the empirical formula.
    If it’s a decimal, multiply them both until you get a whole number
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11
Q

Empirical to molecular formula

A

Need to know the actual mass of the compound and divide that by the molar mass of the empirical formula to get the multiplier

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12
Q

Conservation of matter

A

Matter can be changed but not created or destroyed

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13
Q

What is the base rule for balancing equations?

A

Conservation of matter

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14
Q

Pointers for balancing difficult equations

A

time
2.Firstbalanceelementsthatarecombinedandthatappearonlyonceoneachsideofthe
equation.
3.Ifpolyatomicionappearsonbothsidesoftheequationinexactlythesameway,balance
thepolyatomicionasasingleunit.
4.BALANCEHYDROGENANDOXYGENATOMSLAST.
5.DON’TFORGETTOCHECKATTHEEND!!!!

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15
Q

Chemical reaction formula

A

Reactants➡️products

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16
Q

➡️

A

Yields

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17
Q

Reactants

A

Original substances that react together

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18
Q

Products

A

Result of reaction of reactants

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19
Q

What do you always have to write after the reactants

A

State of matter symbols

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20
Q

State of matters symbols

A

(l) iquid
(s) olid
(g) as
(aq) ueous

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21
Q

Aqueous

A

Dissolved in water

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22
Q

Indications of a chemical reaction

A 
Heat and light
Color change
Odor change 
Gas/production of bubbles
Formation of precipitate
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23
Q

Precipitation

A

cause (a substance) to be deposited in solid form from a solution

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24
Q

5 types of chemical reactions

A
  1. Synthesis (Composition)
    2.Decomposition
    3.SingleReplacement
    (Displacement)
    4.DoubleReplacement
    (Displacement)
    5.Combustion
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25
Synthesis
2 or more substances combine to form a new compound Commonly exothermic a + b--->ab
26
Decomposition
A single compound undergoes a reaction producing two or more simpler substances Commonly endothermic ab-->a+b
27
Which chemical reaction is the opposite of synthesis
Decomposition
28
When does decomposition usually take place?
When energy is added in the form of heat or electricity
29
Single replacement
One element replaces a similar element in a compound Commonly exothermic a + bx-->b + ax
30
Double replacement
The ions of two compounds exchange places in an aqueous solution to form two new compounds ax + by-->ay + bx
31
What are the usual properties of the compounds in double replacement
One compound is usually a precipitate or molecular compound, usually water. The other one is often soluble and remains dissolved in the solution.
32
Precipitate
Insoluble gas that bubbles out of the solution
33
Combustion
Substance combining with oxygen releasing a large amount of energy, heat, light Commonly very exothermic reactant + O2 (g) --> products (+ energy)
34
Activity
Ability of element to react
35
The higher the activity, the___
Easier it reacts
36
Activity series
a list of elements organized according to their activities from highest to lowest
37
What are activity series based on?
Experiment
38
What does activity series help with?
will help tell us whether a reaction will occur!
39
How to use Activity series to predict a single replacement reaction
So, an element that is higher in the activity series will replace an element that is lower than it, but an element that is lower will NOT replace an element that is higher
40
Exothermic
Heat is produced from the reaction
41
Endothermic
require heat/heat is a reactant in the reaction
42
Stoichiometry
The study of the quantitative relationships between reactants and products in a chemical reaction
43
What do balanced chemical reactions do?
Tell us how many moles of each reactant are needed for the reaction and how many moles of the products are formed
44
Mole ratio
Conversion factor relating amounts in moles of any two substances involved in a chemical reaction
45
Steps: molar ratio
-Write given first, with units -Determine mole ratio To get the experimental molar ratio, you divide the moles of each reactant that you actually used in the experiment by each other.
46
Limiting reactant
Reactant that is used up completely first in a reaction-limits amount of other reactants that can combine and products that can form
47
Excess reactant
The reactant that isn't completely used up
48
Percent yield
(Actual yield/Theoretical yield)100
49
Actual yield
Measured amount of a product obtained from a reaction
50
Theoretical yield
Maximum amount of product that can be formed from a given amount of reaction
51
Problem 1: given and unknown are amounts in moles
Balance equation Given in mol (mole ratio) *y mol of unknown from the equation/x mol of given from equation (balanced)
52
Problem two: given is amount in mol, unknown is mass in grams
Problem 2: problem 1, convert mol to g
53
Molar mass proportion
G of substance/ mol of substance = molar mass of substance in g/1 mol
54
Given mass in g, unknown amount in mol
Problem 3-convert g to mol, then problem 1
55
Problem 4: given is mass in g, unknown is mass in g
Problem 4: problem 3, then convert mol to g
56
Finding limited reactant
Given equation and x grams of 1 + y grams of 2 Finding the limited reactant: balance equation Convert x grams of 1 and y grams of 2 to mol Multiply given mol of 1 (mol of 2 FROM EQUATION/mol of 1 FROM EQUATION) The answer tells us how many of 2 we would need for the equation If the answer >what we have of 2, 2 is the limiting reactant It the answer < what we have of 2, 1 is the limiting reactant
57
In a limited reactant problem, how do we find how much of product1 is found in grams?
Multiply the given amount of LR in mol by mole ratio(the amount of product1/the amount of the LR), then convert mol to g
58
LR problem: how much of the ER is left over? (Answer mathematically or in words)
Given mol of ER-(Given mol of LR (mol ratio ER/LR) Convert from mol limiting reactant to mol of excess reactant, telling you how much of the excess reactant is used in the equation. Then subtract the amount from the given in mol of the ER.
59
Given the equation, how do you find the number of moles of one reactant required to produce a specific amount of grams of the product?
Convert mol to g for the product in the equation, then divide it by the mass of the product you're trying to get. Divide the reactant by the answer.
60
Which elements can replace which? (activity series!)
in a single replacement reaction, a more reactive (higher) element can replace a less reactive(lower) one, but a less reactive cannot replace a higher one
61
Given x grams of a react with excess b, the actual yield of the product1 is y. What is the percent yield of product 1?
Convert x grams of a to mol Found mol of a (1 mol of product 1 from the equation/1 mol of a)= mol of product 1 Convert to grams, then find percent yield
62
Mole ratio
(Unknown, but from equation/given, but from equation) in mol

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