Charles's Law: Temperature and Volume Relationship in Gases - Prof. Andrew S. Osborne, Study notes of Chemistry

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Chapter 7 Gases

Temperature and Volume

(Charles’s Law)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.

Charles’s Law

In Charles’s law ,  (^) the Kelvin temperature of a gas is directly related to the volume  (^) P and n are constant  (^) when the temperature of a gas increases, its volume increases General, Organic, and Biological Chemistry

Learning Check

Solve Charles’s law expression for T 2. V 1 = V 2 T 1 T 2 General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.

Solution

Solve Charles’s law expression for T 2. V 1 = V 2 T 1 T 2 Cross multiply to give: V 1 T 2 = V 2 T 1 Solve for T 2 by dividing through by V 1 : V 1 T 2 = V 2 T 1 so T 2 = T 1 x V 2 V 1 V 1 V 1 General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.

7

Calculations Using Charles’s Law

(continued)

STEP 2 Solve Charles’s law for V 2

V

1

= V

2 T 1

T

2 V 2

= V

1

x T

2 T 1 Temperature factor decreases T STEP 3 Set up calculation with data: V 2 = 785 mL x 273 K = 729 mL 294 K General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.

A sample of oxygen gas has a volume of 420 mL at a temperature of 18 °C. At what temperature (in °C) will the volume of the oxygen be 640 mL ( P and n constant)?

1. 443 °C
2. 170 °C
3. –82 °C

Learning Check

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.

STEP 2 Solve Charles’s law for T 2 : T 2 = T 1 x V 2 V 1 STEP 3 Substitute values and calculate: T 2 = 291 K x 640 mL = 443 K 420 mL Volume factor increases T = 443 K – 273 K = 170 °C

Solution (continued)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.

Use the gas laws to complete the following statements with 1) increases or 2) decreases. A. Pressure _______, when V decreases. B. When T decreases, V _______. C.Pressure _______ when V changes from 12 L to 4 L D. Volume _______ when T changes from 15 °C to 45 °C.

Learning Check

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.