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Final Notebook

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3. The pressure of nitrogen gas in a light bulb is 60 kPa at 25°C. Calculate the pressure of the gas<br />

when the temperature inside the bulb rises to 167°C after the bulb is lighted up?<br />

Combined gas law<br />

60kPa = P<br />

298K 440K<br />

26400=298*P<br />

P=88.59060403<br />

P=89kPa<br />

The combined gas law makes use of the relationships shared by pressure, volume, and temperature:<br />

the variables found in other gas laws, such as Boyle's law, Charles' law and Gay-Lussac's law. Let's<br />

review the basic principles of these three laws.<br />

Imagine you are a diver, and you begin your dive with lungs full of air. As<br />

you go deeper under water, the pressure you experience in your lungs<br />

increases. When this happens, the air inside your lungs gets squished, so<br />

the volume decreases. This is an example of Boyle's law in action, which<br />

states that the higher the pressure (P), the lower the volume (V), as<br />

shown in this image. Here, k is any constant number.<br />

Have you ever tried putting a balloon in the refrigerator and notice that it<br />

shrinks? As the temperature of the refrigerated balloon decreases, the<br />

volume of the gas inside the balloon also decreases. When you take the<br />

balloon out of the refrigerator, it reverts to its original size, so the opposite is<br />

also true; when the temperature increases, the volume also increases. The<br />

shrinking balloon serves as a demonstration of Charles' law, which states<br />

that the higher the temperature (T), the higher the volume (V).<br />

Imagine yourself driving down a road, which can cause the<br />

temperature to increase within your tires. As a result, the air inside the<br />

tires expands, and the pressure increases. This is an example of Gay-<br />

Lussac's law, which shows the relationship between pressure (P) and<br />

temperature (T) when the volume remains constant; as the<br />

temperature increases, the pressure also increases.<br />

When we put Boyle's law, Charles' law, and Gay-Lussac's law together, we come up with the<br />

combined gas law, which shows that:<br />

<br />

<br />

<br />

Pressure is inversely proportional to volume, or higher volume equals lower pressure.<br />

Pressure is directly proportional to temperature, or higher temperature equals higher pressure.<br />

Volume is directly proportional to temperature, or higher temperature equals higher volume.<br />

Let's take a look at the formula for the combined gas law. Here, PV / T = k shows how pressure,<br />

volume and temperature relate to each other, where k is a constant number.<br />

The formula for the combined gas law can be adjusted to compare two sets of conditions in one<br />

substance. In the equation, the figures for pressure (P), volume (V), and temperature (T) with<br />

subscripts of one represent the initial condition, and those with the subscripts of two represent the<br />

final condition.<br />

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