Balancing Equations, Acids&Bases, Chemical Reactions

Question 1

what is a chemical reaction?

Answer 1

• process in which atoms rearrange to form new substances

- result in chemical changes

Question 2

when do chemical changes occur?

Answer 2

-creation of new substances

Question 3

what are original substances called?

Answer 3

-reactants

Question 4

what are new substances called?

Answer 4

-products

Question 5

how can chemical reactions be written as?

Answer 5

• word equations
• symbolic equations
• balanced equations

Question 6

what is a word equation?

Answer 6

-uses the name of elements and compounds

Question 7

what is a symbolic equation?

Answer 7

• uses the symbols for elements and compounds

- there are two types: skeleton and balanced equations

Question 8

what is a skeleton equation?

Answer 8

• shows formulas of elements/compounds

- only shows which atoms involved but not how many involved

Question 9

what is a balanced chemical equation?

Answer 9

-shows all the atoms and coefficients telling how many molecules and atoms there are

Question 10

what is the point in balancing?

Answer 10

-to ensure the number of each type of atom is the same on both sides (of the reaction arrow)

Question 11

use of coefficients?

Answer 11

-indicates how many of each molecule there is

Question 12

use of aq, s, l, g?

Answer 12

• indicate the state of each compound
• aq:aqueous/dissoved in water
• s:solid
• l:liquid
• g:gas

Question 13

what is the law of conservation of mass?

Answer 13

• is in a closed system

- mass of reactants equals mass of products

Question 14

what happens in the law of conservation of mass?

Answer 14

• no new matter is created or destroyed;atoms are rearranged for the atoms change partners to form new compounds
• number of each atom in reactants equals number of each atom in products

Question 15

what do subscripts show?

Answer 15

-how many atoms of that particular element are present

Question 16

what do brackets show?

Answer 16

• compound is made up of group of elements that appear more than once
• multiply subscript outside the bracket by the subscrip inside the bracket

Question 17

what do you do with a coefficient in a chemical formula?

Answer 17

-multiply the coefficient by the number of atoms of each element

Question 18

what to do when atoms of the same element appear in more than one place on one side of the equation?

Answer 18

-add them together

Question 19

if polyatomic ions look the same on both sides of the equation, what do you do?

Answer 19

-treat them as a group

Question 20

what is the process of going from word equation to skeleton equation called?

Answer 20

-changing chemical names into chemical formulas

Question 21

what to write when diatomic elements are found alone?

Answer 21

-write subscript 2 after them

Question 22

what other elements are never found alone? and what would be written if they were alone?

Answer 22

• phosphorus: P₄

- sulfur: S₈

Question 23

what are acids and bases strengths measured in?

Answer 23

-pH scales

Question 24

what is pH below 7?

Answer 24

-acids (acidic)

Question 25

what is pH above 7?

Answer 25

-bases (basic)

Question 26

what is pH 7?

Answer 26

-neutral

Question 27

what does each step on the pH scale represent?

Answer 27

-jump of 10 times

Question 28

what does the chemical formula of an acid usually start with?

Answer 28

-hydrogen (H)

Question 29

when acids are dissovled in water what happens?

Answer 29

-they release H+ions

Question 30

what are the properties of acids?

Answer 30

• release H+ions
• taste sour
• turn litmus paper red
• conduct electricity
• react with metals
• will burn skin

Question 31

what does the chemical formula of bases usually end with?

Answer 31

-hydroxide (OH)

Question 32

when bases are dissovled in water what happens?

Answer 32

-they release OH-ions

Question 33

what are the properties of bases?

Answer 33

• release OH-ions
• taste bitter
• turn litmus paper blue
• conduct electricity
• are slippery
• will burn skin

Question 34

difference between acids and bases?

Answer 34

-acidic solutions have a higher concetraction of H+ions and basic solutions have a higher concentraction of OH-ions

Question 35

how do you measure the pH of an acid or base?

Answer 35

• chemicals called indicators

- they change colour depending on the pH of the solution they are placed in

Question 36

what is a free element?

Answer 36

• element is not combined with another element of a different type
• can be combined with itself (HOFBrINCl)

Question 37

what are the types of chemical reactions? (6)

Answer 37

• synthesis
• decomposition
• single replacement
• double replacement
• neutralization (acid-base) reaction
• combustion

Question 38

what is synthesis?

Answer 38

• free element combines with another free element to form a compound
• A+B=AB

Question 39

what is decomposition?

Answer 39

• compound breaks up into free elements

- AB=A+B

Question 40

what is single replacement?

Answer 40

• single free element and single compound react
• if A is metal: A+BC=B+AC
• if A is non metal: A+BC=C+AB

Question 41

what is double replacement?

Answer 41

• two compounds react to form two new compounds

- AB+XY=AY+XB

Question 42

what is neutralization (acid-base) replacement?

Answer 42

• special double replacement reaction between acid and base
• products always salt and water
• acid+base=salt+water

Question 43

what is combustion?

Answer 43

• compound containing carbon and hydrogen react with oxygen
• products are always carbon dioxide and water
• CH4+O2=CO2+H2O