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Helium gas with a volume of \(2.60 \mathrm{~L}\) under a pressure of 1.30 atm and at a temperature of \(41.0^{\circ} \mathrm{C}\) is warmed until both the pressure and volume of the gas are doubled. (a) What is the final temperature? (b) How many grams of helium are there? The molar mass of helium is \(4.00 \mathrm{~g} / \mathrm{mol}\).

Short Answer

Expert verified
The final temperature is 628.3 K, and the mass of helium is 0.528 g.

Step by step solution

01

Convert Temperature to Kelvin

The initial temperature is given as \(41.0^{\circ} \mathrm{C}\). To convert it to Kelvin, use the formula: \[ T(K) = T(^{\circ}C) + 273.15 \]. Thus, the initial temperature is: \[ T_1 = 41.0 + 273.15 = 314.15 \mathrm{~K} \].
02

Use the Ideal Gas Law

The Ideal Gas Law is \(PV = nRT\) where \(n\) is the number of moles, and \(R\) is the ideal gas constant. We'll solve for \(n\) using initial conditions. Given: \(P_1 = 1.30 \mathrm{~atm}\), \(V_1 = 2.60 \mathrm{~L}\), \(T_1 = 314.15 \mathrm{~K}\), and \(R = 0.0821 \mathrm{~L}\cdot\mathrm{atm}\cdot\mathrm{mol}^{-1}\cdot\mathrm{K}^{-1}\). Rearrange the equation to solve for \(n\): \[ n = \frac{P_1V_1}{RT_1} = \frac{1.30 \times 2.60}{0.0821 \times 314.15} \].
03

Calculate the Initial Moles

Plug in the values from Step 2 into the equation: \[ n = \frac{1.30 \times 2.60}{0.0821 \times 314.15} \approx 0.132 \mathrm{~mol} \]. This is the number of moles of helium present.
04

Determine the Final Temperature

When both pressure and volume are doubled, the new pressure \(P_2\) is \(2.60 \mathrm{~atm}\) and the new volume \(V_2\) is \(5.20 \mathrm{~L}\). Use the combined gas law: \[ \frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2} \]. Solve for \(T_2\): \[ T_2 = \frac{P_2V_2T_1}{P_1V_1} = \frac{2.60 \times 5.20 \times 314.15}{1.30 \times 2.60} \].
05

Calculate the Final Temperature

Using the equation from Step 4: \[ T_2 = \frac{2.60 \times 5.20 \times 314.15}{1.30 \times 2.60} = 628.3 \mathrm{~K}\]. The final temperature, \(T_2\), is \(628.3 \mathrm{~K}\).
06

Calculate the Mass of Helium

Using the moles calculated in Step 3 and the molar mass of helium: \[ \text{Molar mass of helium} = 4.00 \mathrm{~g/mol} \]. \[ \text{Mass} = n \times \text{Molar mass} = 0.132 \times 4.00 = 0.528 \mathrm{~g} \]. The mass of helium is \(0.528 \mathrm{~g}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Helium Gas Calculations
Helium gas, a noble gas often used in balloons, exhibits ideal gas behavior under standard conditions. In this exercise, we examine helium gas that initially occupies a volume of \(2.60\, \text{L}\) under a pressure of \(1.30\, \text{atm}\) at a temperature of \(41.0^{\circ}\text{C}\). The problem entails calculating the new temperature when both the pressure and volume are doubled, as well as the mass of helium in the system.
First, we convert the given temperature from degrees Celsius to Kelvin because kelvin is the standard unit used in gas calculations. Helium's chemical property of low molar mass \(4.00\, \text{g/mol}\) makes it less dense than most other gases, facilitating its usage in buoyancy-related applications. By employing the Ideal Gas Law and subsequent calculations, we determine the changes in state variables of the helium gas.
Combined Gas Law
The Combined Gas Law is a useful equation that links the initial and final states of a gas under varying conditions of pressure, volume, and temperature. This law is crucial for this exercise, where helium gas's pressure and volume are both doubled.
The Combined Gas Law formula is given as: \[ \frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2} \] In this expression, \(P_1\), \(V_1\), and \(T_1\) are the initial pressure, volume, and temperature, respectively, while \(P_2\), \(V_2\), and \(T_2\) are their final states.
By solving for \(T_2\), the final temperature, we employ the values from the initial and altered states to establish the conditions under which the helium gas reaches equilibrium after the change in pressure and volume.
Mole and Mass Calculations
Calculating the number of moles and consequently the mass of a gas is fundamental in comprehending gas reactions and quantities. Using helium gas, the exercise illustrates calculating moles using the Ideal Gas Law equation \( PV = nRT \), where \( n \) represents moles.
Substituting the known values allows us to simplify: \[ n = \frac{P_1V_1}{RT_1} \]. This gives us the quantity of helium in terms of moles, which is \(0.132\, \text{mol}\).
Subsequent steps involve multiplying the moles of helium by its molar mass \(4.00\, \text{g/mol}\) to derive the mass in grams. These calculations help manifest the physical reality of chemical amounts into measurable quantities, crucial for preparing reactions, understanding yields, and more.
Temperature Conversions in Chemistry
Converting temperatures to Kelvin is an essential process in many chemistry calculations, particularly those involving gases. Kelvin is the absolute temperature scale used in the study of gases because it allows for direct proportional relationships in equations.
The conversion from Celsius to Kelvin is straightforward: add 273.15 to the Celsius measurement. In this problem, the conversion takes place to transform \(41.0^{\circ}\text{C}\) into \(314.15\, \text{K}\).
This new unit becomes fundamental throughout the calculations, enabling seamless usage in equations like the Ideal Gas Law and the Combined Gas Law. Understanding and applying this conversion helps ensure accurate results in chemical computations and analysis, embodying a foundational step in virtually any thermodynamics problem involving gases.

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Most popular questions from this chapter

In a cylinder, \(4.00 \mathrm{~mol}\) of helium initially at \(1.00 \times 10^{6} \mathrm{~Pa}\) and \(300 \mathrm{~K}\) expands until its volume doubles. Compute the work done by the gas if the expansion is (a) isobaric and (b) adiabatic. (c) Show each process on a \(p V\) diagram. In which case is the magnitude of the work done by the gas the greatest? (d) In which case is the magnitude of the heat transfer greatest?

A flask with a volume of \(1.50 \mathrm{~L}\), provided with a stopcock, contains ethane gas \(\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)\) at \(300 \mathrm{~K}\) and atmospheric pressure \(\left(1.013 \times 10^{5} \mathrm{~Pa}\right) .\) The molar mass of ethane is \(30.1 \mathrm{~g} / \mathrm{mol} .\) The system is warmed to a temperature of \(380 \mathrm{~K},\) with the stopcock open to the atmosphere. The stopcock is then closed, and the flask is cooled to its original temperature. (a) What is the final pressure of the ethane in the flask? (b) How many grams of ethane remain in the flask?

A bicyclist uses a tire pump whose cylinder is initially full of air at an absolute pressure of \(1.01 \times 10^{5} \mathrm{~Pa}\). The length of stroke of the pump (the length of the cylinder) is \(36.0 \mathrm{~cm}\). At what part of the stroke (i.e., what length of the air column) does air begin to enter a tire in which the gauge pressure is \(2.76 \times 10^{5} \mathrm{~Pa}\) ? Assume that the temperature remains constant during the compression.

Three moles of an ideal gas are in a rigid cubical box with sides of length \(0.200 \mathrm{~m}\). (a) What is the force that the gas exerts on each of the six sides of the box when the gas temperature is \(20.0^{\circ} \mathrm{C} ?\) (b) What is the force when the temperature of the gas is increased to \(100.0^{\circ} \mathrm{C} ?\)

A cylinder with a piston contains \(0.250 \mathrm{~mol}\) of ideal oxygen at a pressure of \(2.40 \times 10^{5} \mathrm{~Pa}\) and a temperature of \(355 \mathrm{~K}\). The gas first expands isobarically to twice its original volume. It is then compressed isothermally back to its original volume, and finally it is cooled isochorically to its original pressure. (a) Show the series of processes on a \(p V\) diagram. (b) Compute the temperature during the isothermal compression. (c) Compute the maximum pressure. (d) Compute the total work done by the piston on the gas during the series of processes.

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