The Mole

-Equal volumes of different gases had a constant ratio
Relative Mass
-expressed by comparing it mathematically to the mass of another object

Avogadro's hypothesis
-equal volumes of different gases at the same temperature and pressure have the same unmber of particle
-if they have same number of particles, the mass tatio is due to the mass of particle

FORMULA MASS
-total mass of all the atoms in he formula of an ionic compound in atomic mass units
K39.1u+F19.0u =KF58.1u

MOLECULARR MASS
-total mass of all the atoms that make up a molecule of a covalent compound organic compound or a polyyatomic element in atomic mass units
canbon dioxide
C 12.0g+O2 32g=44g

MOLAR MASS
mass of 1 mole of substane and is the same numerical value of atomic mass, formula mass, or molecular mass but expressed in Grams Per Mole
-1mole of oxygen=16.0g/mol
-1mole of carbon=12.0g/mole

the molar atomic mass of an element is the mass of 1 mole that element
the units of molar are grams per mole (g/mole)

Avogadro's number
-the number of particles in 1 mole of any amount of substance
6.022*10 to the 23
-the mole is extremely important to chemists because it allows them to sount atoms and molecules

mole conversions

1. A)conversions from paricles---mole
 Ex:  3.01 x 10^24----particles/moles
         3.01 x 10^24particles  x  1mole/6.022 x 10^23particels =5.00moles

    B)moles---particles
        0.75moles CO2---molecules
        0.75moles x 6.022 x 10^23molecules/1mol = 4.5 x 10^23molecules of CO2

     C)0.75moles CO2---atom of oxygen
         4.5 x 10^23molecules CO2  x  2atoms/1molecules CO2 = 9.0 x 10^23 atoms of oxygen

2.A) conversions from moles----grams
         2.04moles C---grams
         molar mass of C---12g/mole
          2.04moles x 12g/mole = 24.5g of C

    B)grams---moles
       3.45g C ---moles
       3.45g x 1mole/12.0g = 0.288moles

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3 A) particles --mass

        2.78 x 10^22 Fe atoms    x   1mole/6.022 x 10^23    x  55.8g/1mole  = 2.58 g

    B)mass- particles

        20.0g Fe  x 1mole/55.8g  x 6.022 x 10^23particles/1mole = 2.16 x 10^23particle

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Density

Density=Mass/Volume

for Solid:g/cm3
     Liquid: g/ml
     1cm3=1mL

Density of water:1.0g/mL

Dobject>Dliquid---sink
Dobject<Dliquid---float

D=M/V    M=DV   V=M/D

Accuracy & Precision

-Precision: how reproducible a measurement is compared to other measurement
-Accuracy: how close the measurement for average measurement comes to the accepted or real value

Measurement and Uncertainty
-no measurement is exact
-every measurement is a best estimate
-countable number is exact number

Absolute Uncertainty
-expressed in units of measurement, not as a ratio
Method1:
-make at least 3 measurement, calculate the average
-the absolute uncertainty is the largest difference between the average and the lowest and highest.

Ex:
1  15.3g                                                           average: 15.3g
2  15.5g                                                           AU: 15.3 ± 0.2g
3  15.2g
4  11.9g(remove)
5  15.3g

Method2:
determine the uncertainty of each instrument.
always measure to the best precision that you can.

Relative Uncertainty & Significant Figure

RU=AU/estimate uncertainty            Ex: 39.3±0.1g  RU = 0.1/39.3×100%

or using Sig Fig: the last number in the measurement is uncertain   

Significant Figure

-How to wirite the math anseers correctly-

Signifcant Digit
-the last number is uncertain
-E.g.---2.56      2.5(certain) 6(uncertain)
-wirte only one uncertain digits

Detail
-leading zero aren't counted
0.0000001 has 1 sig fig
-zero after decimal are counted
10050 has 5 sig fig
-trailing without decimal point aren't counted
12000000 has 2 sig fig

Exact number
-some quantities are defined as exactly a certain and no rounding require
Rounding Rules
-round the answers of digits using rules similar to math
-Digit   > 5 round up
62.47---62.5
62.43---62.4
62.45000003---62.5
62.4585---62.5