Here we're told that a sample of neon gas exerts a pressure of 1.85 atmospheres inside a cylinder. Some nitrogen gas is also present at a pressure of 500 Torr. What is the total pressure inside the cylinder? So remember, we just learned about the law of partial pressures, which tells us that the total pressure felt inside of a container, or in this case, a cylinder, comes from adding up the partial pressures of each gas present. So in the container, we have neon gas, and we also have nitrogen gas. The total pressure is when you add their partial pressures together.
Now the issue is we don't have the same units for these gases. Neon is in atmospheres, but nitrogen is in Torr. Since atmospheres is a standard unit we usually use for pressure, let's convert Torr into atmospheres. So we're going to have 500 Torr, and remember that for every 1 atmosphere that's 760 Torr. So when we do that, we're going to get our atmosphere value as 0.65789 atmospheres. Take that and plug it in, and when we do that, we're going to get a total pressure of 2.50789 atmospheres. Within our question, 1.85 has 3 significant figures, 500 only has 1 significant figure. Here, if we round to 1 significant figure, this would round up to 3, which is a pretty big jump in terms of our value. So it's just better to go with the 3 significant figures from this 1.85. Again the question isn't asking for the number of significant figures in your final answer, we're doing this as continuous practice in terms of determining significant figures. Again, better to go with 3 significant figures. I know it's not the least number of significant figures, but going from 2.5 to 3 atmospheres is such a big increase. Better just to go with 3 significant figures and then we have 2.51 atmospheres at the end. So now that we've seen this question, let's move on to the next video.