Balancing Equations, Acids&Bases, Chemical Reactions Flashcards
what is a chemical reaction?
- process in which atoms rearrange to form new substances
- result in chemical changes
when do chemical changes occur?
-creation of new substances
what are original substances called?
-reactants
what are new substances called?
-products
how can chemical reactions be written as?
- word equations
- symbolic equations
- balanced equations
what is a word equation?
-uses the name of elements and compounds
what is a symbolic equation?
- uses the symbols for elements and compounds
- there are two types: skeleton and balanced equations
what is a skeleton equation?
- shows formulas of elements/compounds
- only shows which atoms involved but not how many involved
what is a balanced chemical equation?
-shows all the atoms and coefficients telling how many molecules and atoms there are
what is the point in balancing?
-to ensure the number of each type of atom is the same on both sides (of the reaction arrow)
use of coefficients?
-indicates how many of each molecule there is
use of aq, s, l, g?
- indicate the state of each compound
- aq:aqueous/dissoved in water
- s:solid
- l:liquid
- g:gas
what is the law of conservation of mass?
- is in a closed system
- mass of reactants equals mass of products
what happens in the law of conservation of mass?
- 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
what do subscripts show?
-how many atoms of that particular element are present
what do brackets show?
- compound is made up of group of elements that appear more than once
- multiply subscript outside the bracket by the subscrip inside the bracket
what do you do with a coefficient in a chemical formula?
-multiply the coefficient by the number of atoms of each element
what to do when atoms of the same element appear in more than one place on one side of the equation?
-add them together
if polyatomic ions look the same on both sides of the equation, what do you do?
-treat them as a group
what is the process of going from word equation to skeleton equation called?
-changing chemical names into chemical formulas
what to write when diatomic elements are found alone?
-write subscript 2 after them
what other elements are never found alone? and what would be written if they were alone?
- phosphorus: Pā
- sulfur: Sā
what are acids and bases strengths measured in?
-pH scales
what is pH below 7?
-acids (acidic)
what is pH above 7?
-bases (basic)
what is pH 7?
-neutral
what does each step on the pH scale represent?
-jump of 10 times
what does the chemical formula of an acid usually start with?
-hydrogen (H)
when acids are dissovled in water what happens?
-they release H+ions
what are the properties of acids?
- release H+ions
- taste sour
- turn litmus paper red
- conduct electricity
- react with metals
- will burn skin
what does the chemical formula of bases usually end with?
-hydroxide (OH)
when bases are dissovled in water what happens?
-they release OH-ions
what are the properties of bases?
- release OH-ions
- taste bitter
- turn litmus paper blue
- conduct electricity
- are slippery
- will burn skin
difference between acids and bases?
-acidic solutions have a higher concetraction of H+ions and basic solutions have a higher concentraction of OH-ions
how do you measure the pH of an acid or base?
- chemicals called indicators
- they change colour depending on the pH of the solution they are placed in
what is a free element?
- element is not combined with another element of a different type
- can be combined with itself (HOFBrINCl)
what are the types of chemical reactions? (6)
- synthesis
- decomposition
- single replacement
- double replacement
- neutralization (acid-base) reaction
- combustion
what is synthesis?
- free element combines with another free element to form a compound
- A+B=AB
what is decomposition?
- compound breaks up into free elements
- AB=A+B
what is single replacement?
- single free element and single compound react
- if A is metal: A+BC=B+AC
- if A is non metal: A+BC=C+AB
what is double replacement?
- two compounds react to form two new compounds
- AB+XY=AY+XB
what is neutralization (acid-base) replacement?
- special double replacement reaction between acid and base
- products always salt and water
- acid+base=salt+water
what is combustion?
- compound containing carbon and hydrogen react with oxygen
- products are always carbon dioxide and water
- CH4+O2=CO2+H2O
