QCA Cumulative Exam

quantitative analysis

how much of a chemical substance is present

qualitative analysis

what is present

two components of measurement that need to be recorded

number and units

for analog devices, you estimate

one digit beyond the markings

accuracy

close to the target value

precision

trials are close together

random error affects

precision

random error

variable, unpredictable fluctuation that affects individual measurements

systematic error

consistent, repeatable error that shifts all measurements in the same direction

sigfigs - addition

round the answer to the least number of decimal places found in the numbers used in the calculation

sigfigs - multiplication

result should have the same number of significant figures as the number with the fewest significant figures

kilo - k

1 kg = 1000 g

mili - m

1000 mg = 1 g

1000 mL = 1 L

micro - µ

10⁶ µL = 1 L

10⁶ µg = 1 g

random error is

not reducible

random error is expressed as

standard deviation or confidence interval

systematic error affects

accuracy

systematic errors are

reproducible

systematic errors are expressed as

% error

systematic error is commonly caused by

miscalibration, repetition of improper technique, error in method

gaussian distribution

bell curve

± 1 st deviation from the mean

68%

± 2 standard deviations from the mean

95%

± 3 standard deviations from the mean

99.7%

confidence interval

a range of values that include the true population mean at some level of confidence

Grubbs test: if G_calculated > G_table, the point would be

excluded

the Grubbs test helps you to decide whether or not an outlier

should be discarded

Gaussian distributions are caused by

random errors

NH₄⁺

ammonium

OH^-

hydroxide

CH₃COO^-

acetate

ClO^-

hypochlorite

ClO₂^-

chlorite

ClO₃^-

chlorate

ClO₄^-

perchlorate

NO₂^-

nitrite

NO₃^-

nitrate

SO₃^-

sulfite

SO₄^-

sulfate

Cr₂O₇^2-

dichromate

CO₃^2-

carbonate

C₂O₄^2-

oxalate

CrO₄^2-

chromate

PO₄^3-

phosphate

MnO₄^-

permanganate

HCO₃^-

hydrogen carbonate

crystalline solids

long-range order, sharp melting points

amorphous solids

no regular repeating units, melt over range of time

types of crystalline solids

ionic, metallic, molecular, network

ionic solids

metals and nonmetals

→ ionic bonds

physical properties of ionic solids

hard and brittle

→ high melting point

→ good conductor only as liquid

→ poor conductor of heat

often water soluble

metallic solids

metals and metals

→ metallic bonds

physical properties of metallic solids

malleable

→ good electrical and heat conductor

→ range of hardness and melting points

molecular solids

nonmetals and nonmetals

→ LDF, dipole, hydrogen bonds

physical properties of molecular solids

low - moderate melting/boiling point

→ soft

→ poor electrical and hear conductor

network solids

graphite, diamonds, quartz

→ covalent bonds

physical properties of network solids

wide range of hardness + melting point

→ poor electrical conductor (exceptions)

amorphous solids

glass, nylon

→ covalent bonds

physical properties of amorphous solids

noncrystalline

→ wide melting range

→ poor electrical conductor (exceptions)

1 mole is equal to

6.022 × 10²³ atoms/molecules

ionic hydrates

ionic compounds that have H₂O molecules trapped within the crystal lattice

empirical formula

simplest whole number ratio of atoms in a molecule

molecular formula

actual number of atoms of each element in a molecule

solubility depends on

IMFs and other non-covalent interactions

steps to prepare a solution

→ solute is weighed out on analytical balance

→ portion of the solvent is added to volumetric flask

→ mixture is swirled until all of the solute is dissolved

→ additional solvent is added up to the mark on the volumetric flask

if Q > K

a solid is formed

common ion effect

a salt will be less soluble if one of its constituent ions is already present in the solution

le chatliers principle

if a system at equilibrium is disturbed, equilibrium will shift to partially counteract the change