# 250 ml of oxygen gas is collected over water at a pressure of 1.27 atm and a temperature of 16 degrees C. What volume of dry gas will there be at 105 kpa and -22 degrees C?

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The answer is 261 mL, but I don't know how to arrive there. Thanks!!

The answer is 261 mL, but I don't know how to arrive there. Thanks!!

##### 1 Answer

The question involves unit conversions, Dalton's Law of Partial Pressures and Combined Gas Law.

**Caution:** Long answers ahead.

#### Explanation:

We can gather the following information from the **first** sentence:

Here's what we have from the **second** sentence:

Let's handle the unit conversion first. Since the temperature values are given in degree C, we'll need to convert it to Kelvin for use in any Gas Laws. Here's how we do it:

Looks like the pressures are given in 2 different units. Let's convert

As mentioned earlier, the pressure given in the first sentence is not

Looks like

Let's convert that to atm. [1 atm = 760 torr]

Plugging in to the Dalton's Law of Partial Pressures,

Let's update all the values we have so far:

Rearranging Combined Gas Law to find