Chemical Reactions Flashcards
Chemical Change
atoms rearrange themselves to form new substances with different compositions and properties
Physical Change
The form of the substance changes but the composition and identity does not
What are chemical changes and how do they differ from physical changes.
Chemical changes are when a substance is transformed into a new substance, thus it entire composition and properties changes
ex. Rusting of iron
It differs from physical change in the sense that in physical changes the compound itself has the same properties and identity but just has different form.
Chemical equation
Shorthand way of representing a chemical reaction
Reaction –> Products
What must be included when chemical equations?
- States of reactants/products
ex. (s), (l), (g) and (aq) on each atom - Chemical formulas of the compound derived from the name
aqeous
State of reactant/product that means the compound is dissolved in water
ex. NaCl (aq)
Combustion
How do we correctly represent chemical reactions?
- Identify reactants and products
- Reactants –> Products - Write each product and reactant as a chemical formula
- Separate reactants and products
- Indicate states of matter
- Balance the equation
- Ensure the # of atoms for each element is the same on each side
- Do not change the subscripts
- Balance free elements ex. O2, H2 last
- Express coefficients as lowest whole numbers
Stoichiometry
Numerical relationships between chemical amounts in a balanced chemical equation
Decomposition
Carbonate
CO3^2-
Fermentation
Ethanol (alcohol) formula
C2H5OH
What is the balancing order of a combustion reaction
Balance carbon first, than hydrogen and then oxygen last
What is the limited reactant and how is it found
The limited reactant is the reactant found out first
It is the molecule with the lowest mole per coefficient ratio
Divide the moles by their respective coefficient to find the mole per coefficient ratio
The one with the lowest mole/coefficient is the limited reactant
Theoretical yield
is the amount of product that can be formed in a reaction
It is another way to find the limited reactant
Theoretical yield formula
% yield = Actual yield/Theoretical yield x 100
How do you convert from one substance to another using a balanced equation
Multiply the given moles of the substance by the given molar ratio from the balanced equation.
Mole ratio
The ratio of the balanced reaction that demonstrates how much of what reactant caused how much of another
Theoretical yield
the maximum amount of product that could be produced in a chemical reaction based on the limiting reactant, assuming the reaction proceeds perfectly with 100% efficient with no losses
This should exceed the actual yield always
percent error definition and equation
the difference between a measured or experiment value and an accepted or known value, divided by the known value, multiplied by 100%
If you have the percent yield you can subtract the theoretical yield from 100 to get percent error
100 - % yield
Percentage yield
The ratio of actual yield to theoretical yield or what percentage you are close to the theoretical yield (the maximum product you can get from the reactant) considering the limiting reactant amount
Percentage yield = actual yield/theoretical yield x 100
You can find the percent error by subtracting the percentage yield by 100 percent
