我们继续来看美国高考SATII化学专题解析 The Ideal Gas Law，关于SATII化学，如果是为了800分满分做准备，同时各位同学也的确很愿意花时间，当然有老师指导的更好了，建议选择巴郎SAT化学；如果目标不是定的很高，同时时间也不是很充裕，我建议使用普林斯顿SAT化学。

　　The ideal gas law is the most important gas law for you to know: it combines all of the laws you learned about in this chapter thus far, under a set of standard conditions. The four conditions used to describe a gas—pressure, volume, temperature, and number of moles (quantity)—are all related, along with R, the universal gas law constant, in the following formula:

　　PV = nRT

　　where P = pressure (atm), V = volume (L), n = number of moles (mol), R = 0.08206 L · atm/mol · K, and T = temperature (K).

　　Now try an example using the ideal gas law equation.

　　Example

　　A 16.0 g sample of methane gas, CH4, the gas used in chemistry lab, has a volume of 5.0 L at 27ºC. Calculate the pressure.

　　Explanation

　　Looking at all the information given, you have a mass, a volume, and a temperature, and you need to find the pressure of the system. As always, start by checking your units. You must first convert 16.0 g of CH4 into moles: 16.0 g CH41 mol CH4/16.0 g CH4 = 1 mol of methane. The volume is in the correct units, but you must convert the temperature into Kelvins: 27 + 273 = 300K. Now you’re ready to plug these numbers into the ideal gas law equation:

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