Chemical Reactions

Question 1

Chemical Change

Answer 1

atoms rearrange themselves to form new substances with different compositions and properties

Question 2

Physical Change

Answer 2

The form of the substance changes but the composition and identity does not

Question 3

What are chemical changes and how do they differ from physical changes.

Answer 3

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.

Question 4

Chemical equation

Answer 4

Shorthand way of representing a chemical reaction

Reaction –> Products

Question 5

What must be included when chemical equations?

Answer 5

1. States of reactants/products
   ex. (s), (l), (g) and (aq) on each atom
2. Chemical formulas of the compound derived from the name

Question 6

aqeous

Answer 6

State of reactant/product that means the compound is dissolved in water

ex. NaCl (aq)

Question 7

Combustion

Answer 7

Question 7

How do we correctly represent chemical reactions?

Answer 7

1. Identify reactants and products
   - Reactants –> Products
2. Write each product and reactant as a chemical formula
3. Separate reactants and products
4. Indicate states of matter
5. 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

Question 8

Stoichiometry

Answer 8

Numerical relationships between chemical amounts in a balanced chemical equation

Question 9

Decomposition

Answer 9

Question 10

Carbonate

Answer 10

CO3^2-

Question 10

Fermentation

Answer 10

Question 11

Ethanol (alcohol) formula

Answer 11

C2H5OH

Question 12

What is the balancing order of a combustion reaction

Answer 12

Balance carbon first, than hydrogen and then oxygen last

Question 13

What is the limited reactant and how is it found

Answer 13

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

Question 14

Theoretical yield

Answer 14

is the amount of product that can be formed in a reaction

It is another way to find the limited reactant

Question 15

Theoretical yield formula

Answer 15

% yield = Actual yield/Theoretical yield x 100

Question 16

How do you convert from one substance to another using a balanced equation

Answer 16

Multiply the given moles of the substance by the given molar ratio from the balanced equation.

Question 16

Mole ratio

Answer 16

The ratio of the balanced reaction that demonstrates how much of what reactant caused how much of another

Question 17

Theoretical yield

Answer 17

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

Question 18

percent error definition and equation

Answer 18

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

Question 18

Percentage yield

Answer 18

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