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Significant Figures
General or Intro to Chemistry I
Rules for One Value
• 1) numbers 1-9 are significant
• Zeros:
– Before – not significant
– Between – Significant
– End – when there is a decimal any where –
significant
– When there is no Decimal anywhere they are not significant
Can you Follow?
• Determine the number of significant figures:
– A) 0.003204500
Rule 1) 0.003204500 four sig figs
Zeros: Beginning 0.003204500 3 but not sig figs
Between 0.003204500 one sig figs
end 0.003204500 two sig figs because of
decimal
0.003204500 has seven significant numbers
Lets Practice!
• Determine the number of significant figures in
each of the following measurements.
a) 48077 mi 5sig. figs.
b) 56 ml 2sig. figs.
How did you do? Are you
c) 0.0000030g 2 sig. figs.
ready to move on? If not
please go over the rules and
d) 29000. ton 5 sig. figs.
practice till you drop.
e) 15000g/cm3 2 sig. figs.
f) 4.0100x10-4 5sig. figs.
Rules for More than One Value
• When adding or subtracting the answer reflects
the value with the least number after the
decimal.
• When Multiplying of dividing the answer reflects
the value with the least significant number.
• When there is a combination always follow the
order PEMDAS (Parenthesis, Exponents,
Multiplication or Division, Addition or
Subtraction).
Can You Follow?
• Addition/Subtraction Multiplication/Division
89.332
2.8 X 4.5039=
+ 20.0##
12.61092
109.332
Answer: 13.
answer: 109.3
Please be aware that both answers always consider the least number
of value but only Multiplication/Division followed significant figures.
Did you also notice that addition /subtraction reported more values
that the numbers given?
Lets Practice!
Carry out the following mathematical Operations
and express answers in correct significant figures.
a) (4.20x10−4) +
-4
(3.564x10−11) =4.20000x10
= 4.20x10-4
b) (0.00950) x (8.501x107) ÷ 3.1425x10−11 = 2.56991x1016
c) (2.420𝑔 + 15.6𝑔) ÷ 4.8𝑔 =
3.7541667
= 3.8
Warning: When rounding some professors follow the following rule
It the digit remove is 5, the preceding number is increased by 1 if is add
and unchanged if it is even
= 2.57x1016
Hope that Help!
• Practice the rules when ever you have a chance and you
will do great! Practicing over and over and over…. is the
way to remember!
If you still have questions please stop by the Science Tutoring
Lab.
LOH 230