Honors Chemistry – Chapter 1 (Gases) Review

A comprehensive set of question-and-answer flashcards covering the key principles, laws, and definitions from the Chapter 1 Gases Review in Honors Chemistry.

What language does the word “gas” originate from?

Dutch (the word “gaos”).

Approximately what percentage of Earth’s atmosphere is nitrogen?

78 %.

Approximately what percentage of Earth’s atmosphere is oxygen?

21 %.

Which fundamental property explains why a gas fills its entire container?

Gases expand to fill the entire volume available.

Why are most gases difficult to see or smell?

Most gases are colorless and odorless.

How does the density of gases compare to that of liquids and solids?

Gases have low density.

How do gases form solutions with one another?

They mix uniformly, distributing evenly throughout the container.

Which two variables mainly cause a gas’s volume to change?

Temperature and pressure.

What is atmospheric pressure?

The force exerted on objects by the air in Earth’s atmosphere.

Which instrument measures atmospheric pressure?

A barometer.

What value is defined as standard atmospheric pressure in mm Hg?

760 mm Hg.

Which device is commonly used to measure the pressure of a confined gas sample?

A manometer.

The pressure unit ‘torr’ honors which Italian scientist?

Evangelista Torricelli.

According to Boyle’s work, how are pressure (P) and volume (V) related for a fixed amount of gas at constant temperature?

They are inversely related (P × V = constant).

State the mathematical form of Boyle’s Law used for two sets of conditions.

P₁V₁ = P₂V₂.

According to Charles, how are volume (V) and absolute temperature (T in K) related at constant pressure and moles?

They are directly proportional (V ∝ T).

Write the equation form of Charles’s Law.

V₁⁄T₁ = V₂⁄T₂.

According to Gay-Lussac, how are pressure (P) and absolute temperature (T in K) related at constant volume and moles?

They are directly proportional (P ∝ T).

Write the equation form of Gay-Lussac’s Law.

P₁⁄T₁ = P₂⁄T₂.

Give the expression for the Combined Gas Law.

P₁V₁⁄T₁ = P₂V₂⁄T₂.

Define Standard Temperature and Pressure (STP) numerically.

273 K and 1 atm (101.3 kPa, 760 mm Hg, 760 torr, 14.7 psi, 1.01 bar).

Under what general conditions do gases behave most ideally?

High temperature and low pressure.

State Assumption #1 of the Kinetic Molecular Theory (KMT) for an ideal gas.

Gas particles occupy no volume compared with the container’s volume.

State Assumption #2 of the Kinetic Molecular Theory for an ideal gas.

Gas particles exert no attractive or repulsive forces; collisions are perfectly elastic.

Write the Ideal Gas Law equation and identify each symbol.

PV = nRT, where P = pressure, V = volume in L, n = moles, R = gas constant, T = temperature in K.

Give the numerical value and units of R when pressure is in atmospheres.

0.0821 L·atm·mol⁻¹·K⁻¹.

According to Avogadro’s Hypothesis, what volume does one mole of any gas occupy at STP?

22.4 L.

Write the “Kitty Cat Equation” for molar mass using density.

Molar mass = dRT⁄P.

Define ‘vapor’ in the context of chemistry.

The gaseous portion of a substance that exists above its liquid phase.

What is vapor pressure?

The pressure exerted by a substance’s vapor when it is in equilibrium with its liquid phase.

How do weak intermolecular forces affect vapor pressure?

Weaker forces result in higher vapor pressures because particles escape the liquid more easily.

Define the boiling point of a liquid.

The temperature at which its vapor pressure equals the external (atmospheric) pressure.

How does elevation affect the boiling point of water?

At higher elevations, atmospheric pressure is lower, so the boiling point decreases.

State Dalton’s Law for the total pressure of a gas mixture.

Ptotal = PA + PB + PC + …

How do you calculate the partial pressure of one component using mole fraction?

Pcomponent = Ptotal × (ncomponent ⁄ ntotal).

What is diffusion in gases?

The movement of gas particles from regions of higher concentration to lower concentration, leading to uniform mixing.

State Graham’s Law relating the rate of diffusion of two gases.

Rate₁⁄Rate₂ = √(M₂⁄M₁), where M = molar mass.

Give the expression for the root-mean-square speed (u_rms) of a gas.

u_rms = √(3RT⁄M), with M in kg mol⁻¹.

Define effusion.

The passage of gas particles through a tiny opening into an evacuated space.

According to Graham’s Law, how do molar masses affect effusion rates?

Lighter gases effuse faster; Rate₁⁄Rate₂ = √(M₂⁄M₁).

State the two van der Waals correction factors and what they adjust for.

‘a’ corrects for intermolecular attractions (pressure), ‘b’ corrects for finite molecular volume (volume).

How does increasing pressure affect the deviation of real gases from ideal behavior?

Higher pressure increases deviations, especially for heavier gases.

How does decreasing temperature affect the ideality of real gases?

Lower temperatures cause gases to behave less ideally (deviation increases).