Che310

Length

Meter (m)

Mass

Kilogram (kg)

Time

Seconds (s)

Temperature

Kelvin (K)

Amount of substance

Mole (mol)

Luminous intensity

Candela (cd)

Mega-

10^6 (M)

Kilo-

10³ (k)

Centi-

10^(-2) (c )

Milli-

10^(-3) (m)

Micro-

Micro-

10^(-6) (μ) (”mu”)

Nano-

10^(-9) (n)

Pico-

10^(-12) (p)

Masserini’s Main Mandate

Calculate moles= 6.023•10^(23) mol^(-1) Avogadro’s constant

Avogadro’s constant

6.023•10^(23) mol^(-1)

Formula Weight

Sum of the atomic weights of all the atoms of a species. In g/mol

Molecular Weight

In g/mol. May be used if the chemical species is a molecule (2 or more non-metals)

Molarity

M; mol/L = 1mmol/1ml

Molality

m; mol/kg = 1mmol/1g

Mass

An unchanging measure of the quantity of matter in an object

Weight

The force of attraction between an object and its surroundings (principally Earth). Because gravitational attraction varies with geographical location, an object’s weight depends on where you weigh it.

Relation between weight and mass

w=m•g

w= weight of an object

m= its mass

g= acceleration due to gravity

1 mol (in mmol)

= 1000 mmol

1 mmol (in mol)

0.001 mol

Analytical molarity

Aka. Formality, F

Specifies a recipe by which a soln is prepared

Error

Difference between accepted and measured value.

Also to describe uncertainty in the measurement

Replicates

Measurements carried out in the same way

N

Number of measurements

Mean

x

Central value, arithmetic mean, average

Sum of replicate measurements/N

Median

Middle result

x(t)

True or accepted value

Precision

Reproducibility of measurements

Closeness of results

Accuracy

Closeness of measurements to the true value

Expressed as error

Absolute error

E = x(i) (measured value) - x(t) (true value)

Can be + or -

Relative Error

E(r ) = ( (xi - xt) / xt ) •100%

Random/Indeterminate error

Affects precision

Can never be entirely eliminated

Causes data to be scattered symmetrically around a mean value

Gross errors

Large errors resulting from human error

Can be high or low

Outliers

Result from gross error

Systematic/ determinate error

Affect accuracy

Causes the mean to differ from the accepted value

Lead to biases (low value = -; high value = +)

Instrumental, method, personal