CHEM 121 MODULE 2 STUDY GUIDE
1. empirical formula (how to find it %)
Answer 1. divide each element % by the atomic weight of the elem.
2. divide all numbers by smallest number in the group (including itself) to get a second set of numbers
3. round up to nearest whole number, that is your formula
--if any of the numbers ends in a decimal that is equal to a fraction, multiply all numbers by the denominator of that
fraction and that will be your formula (exp. 0.25=1/4, 0.33=1/3, 0.5=1/2, 0.6=2/3, 0.75=3/4... exp. 3.5= 3(1/2)= 7/2=
multiply all numbers by 2
4. each whole number is the number of atoms of the element in the formula
2. balancing chemical equations
Answer 1. dont change the subscript #'s
2. balance oxygen last, hydrogen second to last, and other atoms first
3. coeflcients can only be placed in front of formulas, and applies to all atoms in the compound
4. when counting, total # of atoms of that element is equal to coeflcient*element subscript*parenthesis subscript
3. my grammy is bigger than a mole
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12
, Answer grams are larger than moles. so when finding an answer the grams (#) should always be
larger than the moles (#)
4. ionic equation
Answer tells what is actually happening at ionic level in solution
5. net ionic equation
Answer actual reaction that occurs at ionic level, spectator ions (ions that appear on both sides in the same
form) are cancelled out to het the net
6. 5 types of reactions
Answer 1. combination reactions
2. decomposition reactions
3. combustion reactions
4. double replacement reactions
5. single replacement reactions
7. combination (synthesis) reactions
Answer reaction in which single product is formed from multiple reac- tants
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12
1. empirical formula (how to find it %)
Answer 1. divide each element % by the atomic weight of the elem.
2. divide all numbers by smallest number in the group (including itself) to get a second set of numbers
3. round up to nearest whole number, that is your formula
--if any of the numbers ends in a decimal that is equal to a fraction, multiply all numbers by the denominator of that
fraction and that will be your formula (exp. 0.25=1/4, 0.33=1/3, 0.5=1/2, 0.6=2/3, 0.75=3/4... exp. 3.5= 3(1/2)= 7/2=
multiply all numbers by 2
4. each whole number is the number of atoms of the element in the formula
2. balancing chemical equations
Answer 1. dont change the subscript #'s
2. balance oxygen last, hydrogen second to last, and other atoms first
3. coeflcients can only be placed in front of formulas, and applies to all atoms in the compound
4. when counting, total # of atoms of that element is equal to coeflcient*element subscript*parenthesis subscript
3. my grammy is bigger than a mole
1/
12
, Answer grams are larger than moles. so when finding an answer the grams (#) should always be
larger than the moles (#)
4. ionic equation
Answer tells what is actually happening at ionic level in solution
5. net ionic equation
Answer actual reaction that occurs at ionic level, spectator ions (ions that appear on both sides in the same
form) are cancelled out to het the net
6. 5 types of reactions
Answer 1. combination reactions
2. decomposition reactions
3. combustion reactions
4. double replacement reactions
5. single replacement reactions
7. combination (synthesis) reactions
Answer reaction in which single product is formed from multiple reac- tants
2/
12
