Chapter 1-6 Flashcards: Gas Pressure, Ideal Gas, and Avogadro's Number

A set of practice Q&A flashcards covering pressure, the ideal gas model, Avogadro's number, moles, and related calculations from the lecture notes.

What is the basic definition of pressure in the P = F/A formula and its SI unit?

Pressure equals force divided by area (P = F/A). SI unit is the pascal (Pa), where 1 Pa = 1 N/m^2. The area must be in square meters.

Why does a bed of nails not pop a balloon, whereas a single nail would?

Because the same push (force) is spread over hundreds of nail tips, greatly reducing the pressure on any one point; pressure, not total force, decides whether the balloon skin breaks.

List the four main assumptions of the ideal gas model.

1) Particles have negligible (zero) volume, 2) No intermolecular forces between particles, 3) Particles are in constant, random motion at high speeds, 4) Collisions are perfectly elastic (no energy loss).

Under what conditions does a real gas behave most like an ideal gas?

High temperature and low pressure, when particles move fast and are far apart, minimizing interactions and finite-size effects.

What is Avogadro's constant and its value?

Avogadro's constant Na = 6.02 × 10^23 particles per mole.

What is a mole in chemistry?

A mole is the amount of substance containing exactly Na = 6.02 × 10^23 particles; it is a bridge between microscopic and macroscopic worlds.

What is the relationship between the total number of particles N, the number of moles n, and Avogadro's constant Na?

N = n × Na (and conversely n = N ÷ Na).

If a container holds 3.01 × 10^24 helium atoms, how many moles are present?

n = N ÷ Na = (3.01 × 10^24) ÷ (6.02 × 10^23) = 5.0 moles.

How many particles are in 11 moles of gas?

N = n × Na = 11 × 6.02 × 10^23 = 6.622 × 10^24 particles.

How do you convert an area from cm^2 to m^2?

Divide by 10,000 (since 1 m^2 = 100 cm × 100 cm = 10,000 cm^2).

Calculate the pressure for a 250 N weight on a base measuring 50 cm by 40 cm.

Area = 0.50 m × 0.40 m = 0.20 m^2. P = F/A = 250 N / 0.20 m^2 = 1250 Pa.

Using the elephant example, a 40,000 N force on an area of 2,500 cm^2 gives what pressure in pascals?

Area in m^2 = 2,500 cm^2 ÷ 10,000 = 0.25 m^2. P = 40,000 N ÷ 0.25 m^2 = 160,000 Pa.

What is an elastic collision in the context of the ideal gas model?

A collision in which kinetic energy is conserved; no energy is lost during the collision.

Why are high temperature and low pressure the conditions that make the ideal gas model work best?

High temperature increases kinetic energy so particles move fast and don’t feel weak attractions; low pressure means particles are far apart, making their size and interactions negligible.

What happens to real gases under very low temperatures and very high pressures according to the notes?

The gas deviates from ideal behavior; intermolecular forces become significant, and the simple model no longer accurately describes the gas (possible condensation, non-ideal effects).

What is the key idea behind the ‘puzzle’ about pressure on a bed of nails?

Pressure depends on how concentrated the force is; spreading the force over many points reduces pressure and prevents popping the balloon.

What is the core takeaway about the mole and Avogadro's number from the notes?

The mole links macroscopic measurements to microscopic particles via Avogadro’s constant; N = n × Na, where Na ≈ 6.02 × 10^23.