Ch.6 - Gases

Tro - Chemistry: A Molecular Approach 6th Edition

Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217Not the one you use?Change textbook

Tro 6th Edition

Ch.6 - Gases

Problem 76

Chapter 6, Problem 76

The air in a bicycle tire is bubbled through water and collected at 25 °C. If the total volume of gas collected is 5.45 L at a temperature of 25 °C and a pressure of 745 torr, how many moles of gas were in the bicycle tire?

Verified step by step guidance

Identify the given values: Volume (V) = 5.45 L, Temperature (T) = 25 °C, Pressure (P) = 745 torr.

Convert the temperature from Celsius to Kelvin using the formula: T(K) = T(°C) + 273.15.

Convert the pressure from torr to atm using the conversion factor: 1 atm = 760 torr.

Use the Ideal Gas Law equation: PV = nRT, where R is the ideal gas constant (0.0821 L·atm/mol·K).

Rearrange the Ideal Gas Law to solve for the number of moles (n): n = PV / RT, and substitute the known values to find n.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ideal Gas Law

The Ideal Gas Law is a fundamental equation in chemistry that relates the pressure, volume, temperature, and number of moles of a gas. It is expressed as PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature in Kelvin. This law allows us to calculate the number of moles of gas when the other variables are known.

Units of Pressure

Pressure can be measured in various units, including torr, atm, and pascals. In this question, the pressure is given in torr, which is a common unit for measuring gas pressure. To use the Ideal Gas Law effectively, it is important to ensure that all units are consistent, particularly converting pressure to atmospheres if necessary, as the ideal gas constant R is often expressed in terms of atm.

Temperature Conversion

Temperature must be expressed in Kelvin when using the Ideal Gas Law. The conversion from Celsius to Kelvin is done by adding 273.15 to the Celsius temperature. In this case, the temperature of 25 °C must be converted to Kelvin (25 + 273.15 = 298.15 K) to ensure accurate calculations when applying the Ideal Gas Law.

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