Lorenzo Romano Amedeo Carlo Avogadro Ch 3.2 Notes: Dimensional Analysis and Lorenzo Romano Amedeo Carlo Avogadro

Reminders about Kelvin K = °C + 273 °C = K – 273 Absolute Zero: 0 on the Kelvin scale, has not yet been achieved and has been deemed not possible. Fun Fact: In Celsius and Fahrenheit, absolute zero is -273.15°C and -459.67°F

Dimensional Analysis

This Not That

Conversion Factors Fractions in which the numerator and denominator are EQUAL quantities expressed in different units Example: 1 in. = 2.54 cm Factors: 1 in. and 2.54 cm 2.54 cm 1 in.

Learning Check 1. Liters and mL 2. Hours and minutes Write conversion factors that relate each of the following pairs of units: 1. Liters and mL 2. Hours and minutes 3. Meters and kilometers

How many minutes are in 2.5 hours? Conversion factor 2.5 hr x 60 min = 150 min 1 hr cancel By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers!

Sample Problem You have $7.25 in your pocket in quarters. How many quarters do you have? 7.25 dollars 4 quarters 1 dollar = 29 quarters X

You Try This One! If Jacob stands on Spencer’s shoulders, they are two and a half yards high. How many inches is that?

b) 244 cm c) 24.4 cm Learning Check a) 2440 cm A rattlesnake is 2.44 m long. How long is the snake in cm? a) 2440 cm b) 244 cm c) 24.4 cm

b) 244 cm 2.44 m x 100 cm = 244 cm 1 m Solution A rattlesnake is 2.44 m long. How long is the snake in cm? b) 244 cm 2.44 m x 100 cm = 244 cm 1 m

Amedeo Avogadro A well known Italian scientist who discovered that equal volumes of gases under standard temperature and pressure (STP 0°C, 1atm) is composed of 6.022x10^23 molecules. This is known as Avogadro’s number, commonly referred to as a mol.

Avogadro’s Number (aka mol) 6.022x10^23 = 1 mol NEED TO KNOW Avogadro’s Number (aka mol) 6.022x10^23 = 1 mol Similar to how we count dozens (12), a mol is simply another way to count 6.022x10^23. 6.022x10^23 molecules 1mol 1 mol 6.022x10^23 molecules

Let’s Practice Together 1) How many molecules in 2.5 mols? 2)How many mols are in 8.09x10^25 molecules of pure oxygen gas? 3) If there is 1 mol of a gas contains 22.4 L at standard temperature and pressure (0°C, 1atm), how many liters are in 1.5 mols at STP?

Let’s Practice Together 1) How many molecules in 2.5 mols? 1.5x10^24 molecules 2)How many mols are in 8.09x10^25 molecules of pure oxygen gas? 134.4 mols 3) If there is 1 mol of a gas contains 22.4 L at standard temperature and pressure (0°C, 1atm), how many liters are in 1.5 mols at STP? 33.6 L