The Gas Laws. Types of Variation. What type of variation is it? Write the equation of the line.

Transcription

1 The Gas Laws 1) Types of Variation 2) Boyle's Law + P V Investigation 3) Charles' Law + T V Thought Lab 4) Lussac's Law + T P Investigation 5) The Combined Gas Law 6) Avogadro and the Universal Gas Law Types of Variation What type of variation is it? Write the equation of the line.

2 Boyle s Law Robert Boyle (Irish Chemist, ) studied pressure volume relationships. Boyle s Law the volume of a given amount of gas, at a constant temperature, varies inversely with the applied pressure. V=k P P=k V ASSUME: constant temp. and moles of gas. According to Boyle's Law: if volume decreases to half, pressure increases by a factor of 2. if volume decreases to 1/3, pressure increases by a factor of 3. When volume of the container decreases, gas particles get closer together and exert more force on the walls of the container. (See fig on p. 432) When temp. and amount of gas is constant P 1 V 1 = P 2 V 2 Ex. p.434 #1 A 50.0 cm 3 sample of nitrogen gas is collected at kpa. If the volume is reduced to 5.0 cm 3, and the temperature remains constant, what will the final pressure of the nitrogen be? P1= kpa V1= 50.0 cm 3 P2=? V2= 5.0 cm Homework 3 p. 435 # 2, 3, (top) 2, 3, 4, 5, 6 (bottom) P1V1 = P2V2 P2 = P1V1 V2 = (101.3 kpa)(50.0 cm 3 ) 5.0 cm 3 = 1.0 x 10 3 kpa

3 Charles' Law Volume and Temperature of Gasses p. 441 Charles' Law and Kelvin Temperatures Thought Lab Temperature ( ) Volume ( ) Volume 273C Temperature Temperature is a measure of the average kinetic energy of the molecules in a substance. What happens when we increase the temperature? properties

4 French scientist Jaques Charles ( ) was interested in hot air balloons and studied how an expandable container reacts to temperature changes. He found that if a gas was heated from 0 C to 273 C, it's volume would double. He also noticed that the x intercept on all of his graphs was 273 C. In 1848 Lord Kelvin realized the significance of this finding. At 273 C In real life gasses will condense and change state at temperatures close to 273 C. Kelvin used Charles' finding as the basis of the Kelvin temperature scale. T K = C Charles' Law The volume of a fixed mass (or number of moles) of gas is proportional to its temperature if pressure is held constant (and temperature is in Kelvin). Homework p.446 # 5a, 6a, 8,9

5 p.447 Gay Lussac's Law The pressure of a fixed amount of gas, at constant volume, is directly proportional to it's Kelvin temperature. P T P = kt P = k T P 1 = P 2 T 1 T 2 Ex. p.450 # 14 At 18C a sample of helium gas stored in a metal cylinder exerts a pressure of 17.5 atm. What will the pressure become if the temperature increases to 40C? (answer 18.8 atm) Gas Laws ALWAYS SWITCH TO Kelvin Try p. 449#13

6 Combined Gas Law Boyle's Law Charles' Law Gay Lussac's Law Boyle's Law Charles' Law Gay Lussac's Law

7 Ex. p. 457#17 A sample of gas has a volume of 150mL aat 260K and 92.3 kpa. What will the new volume be at 376K and 123 kpa? (answer 163mL) Do p. 457 # (answers on p ) Gasses HW List So Far Boyle p.435 #2,3 (top) #2,3,4,5,6 (bottom)+graphing Assignment Charles p.446#5a,6a,8,9 + Thought Lab Gay-Lussac p.450#15 p.449#13 + Graph Combined p.457# 20,21 +18,19 p.446 #8 A sample of nitrogen gas surrounding a circuit board occupies a volume of 300mL at 17C and 100 kpa. What volume will the nitrogen occupy at 100.0C if the pressure remains constant?

8 p.457#17 A sample of gas has volume of 150 ml at 260K and 92.3 kpa. What will the new volume be at 376 K and 123 kpa.

9 Gay Lussac was confused by the volume of gas reactants and products in chemical reactions 2 volumes H volume O 2 = 2 volumes H 2 O 3 volumes H volume N 2 = 2 volumes NH 3 1 volume H volume Cl 2 = 2 volumes HCl Avogadro recognized that these volume ratios were the same as the mole rations 2 moles H moles O 2 = 2 moles H 2 O 3 moles H moles N 2 = 2 moles NH 3 1 moles H moles Cl 2 = 2 moles HCl

10 Avagadro's Hypothesis Avagadro proposed that equal volumes of ideal gasses at the same temperature and pressure contain the same number of moles of gas. (or the same number of molecules) This means that for a balanced chemical equation, the ratio of the volumes of the gasses equals the ratio of the moles of gasses. coefficients T = 0C P= 1 atm At standard temperature and pressure (STP) a mole of gas occupies 22.4 L. The space occupied by 1 mole of gas is called the molar volume. T = 0 C P= 1 atm Law of Combining Volumes In a chemical reaction the ratio of the volumes of gas involved in the reaction equals the molar ration in the balanced chemical equation. Ex. p.482#5 A balloon contains 2.0 L of helium gas at STP. How many moles of helium are present? (0.089 mol) p.482#6,7

11 Ideal Gas Law Avagadro Charles' Law Boyle's Law V= volume n = # moles T = temperature P = pressure R= gas law constant HOMEWORK p # HOMEWORK p # p.487 # L of ammonia gas is a container holds 2.17 mol at 206 kpa. What is the temperature in the container?

12 p.488 #13

13 p 486 Sample Problem A cylinder of laughing gas has diameter 23.0 cm and height 140 cm. THe pressure is 108 kpa and the temperature is 294 K. How many grams of laughing gas are in the cylinder? 4.00L of ammonia gas in a container holds 2.17mol at 206kPa. What is the temperature inside the container? HOMEWORK p # 12 14

14 p.488 # 13 How many kg of chlorine gas are contained in 87.6 m 3 at 290K and 2.4 atm? Charles' Law Glove Experiment robertburkottawa (4 min) Getting to Absolute Zero (11 min) Nobel prize in Physics BBT (2 min) Nova: Absolute Zero (1 hr 43 min) 7:34 Boyle 15:30 Temperature Pressure Experiments