ACS Exam concepts

What experiment discovered the nucleus of the atom?

Rutherford's gold foil

What is Avogadro's number?

6.022 × 10^23

Which gas law combines Boyle's and Charles's laws?

Combined Gas Law

What formula is used to calculate enthalpy change from heats of formation?

ΔH = ΣΔHf(products) - ΣΔHf(reactants)

What does a buffer solution do?

Maintains pH when small acid/base is added

What type of reaction involves electron transfer?

Redox

How do you calculate free energy from equilibrium constant?

ΔG° = -RT ln K

What type of solid has delocalized electrons that conduct electricity?

Metallic

In a first-order reaction

what plot gives a straight line?, ln[A] vs. time

What does Le Châtelier's principle predict?

The direction equilibrium shifts with stress

What equation is used for energy of an electron transition in hydrogen?

ΔE = -Rh(1/nf² - 1/ni²)

How many atoms are in a face-centered cubic unit cell?

4

What is the ideal gas law?

PV = nRT

How is enthalpy of reaction calculated from heats of formation?

ΔH = ΣΔHf(products) - ΣΔHf(reactants)

What order reaction has a half-life independent of concentration?

First order

What plot gives a straight line for a second-order reaction?

1/[A] vs. time

What does a phase diagram show at triple point?

All three phases coexist

What is the expression for the equilibrium constant?

K = [products]/[reactants]

Which electrode is the site of reduction in an electrochemical cell?

Cathode

What is the trend of ionization energy across a period?

Increases

What is the formula for calculating molarity?

M = n/V

What is the van't Hoff factor (i) used for?

Colligative properties

Which intermolecular force is strongest?

Hydrogen bonding

What does Hess's law state?

ΔH of reaction is same whether in one step or many

What is the relationship between ΔG° and K at equilibrium?

ΔG° = -RT ln K

What is the unit of the rate constant for a second-order reaction?

M⁻¹·s⁻¹

What instrument is used to measure solution absorbance?

Spectrophotometer

Which electrode is the anode in a galvanic cell?

Site of oxidation

Which type of solid has high melting pointpoor conductivity, and is often hard?

Ionic

What is Le Châtelier's principle about pressure and gases?

Shifts to fewer moles of gas

What is the formula for density?

d = m/V

What is the standard enthalpy of formation for elements in their standard state?

0

Which gas effuses faster

lighter or heavier?, Lighter

What does the collision model emphasize for reactions?

Proper orientation and sufficient energy

What is the formula for pH?

pH = -log[H⁺]

What is Kw at 25 °C?

1.0 × 10^-14

What type of salt solution can be acidic or basic?

Salt hydrolysis

What is the strongest oxidizing agent?

Highest E° value

What property increases across a period and decreases down a group?

Electronegativity

What is the definition of accuracy in measurement?

Closeness to true value

What is the formula for percent yield?

(actual/theoretical) × 100

What is the gas constant R in L·atm/mol·K?

0

Which quantum number describes orbital shape?

l

What is the molecular geometry of CH4?

Tetrahedral

What type of reaction is CaCO3 → CaO + CO2?

Decomposition

Which process is endothermic?

Melting

What does a catalyst do?

Lowers Ea

What is the SI unit for pressure?

Pa

What is the empirical formula of a compound with 40% C, 6.7% H, 53.3% O?

CH2O

What is the definition of precision?

Reproducibility of results

What law relates pressure and temperature directly?

Gay-Lussac's law

Which phase is least dense in most substances?

Gas

What does the band gap differentiate?

Metals, semiconductors, insulators

What is the relationship between frequency and wavelength?

c = λν

What is Planck's constant h?

6.626 × 10^-34 J·s

What is the charge of a proton?

1

What is the main difference between ionic and covalent bonds?

Electron transfer vs. sharing

Which has stronger intermolecular forces: H2O or CO2?

H2O

What is the common ion effect?

Reduced ionization by added salt

What is the law of conservation of mass?

Matter is neither created nor destroyed