A container has a volume of #4 L# and holds #3 mol# of gas. If the container is expanded such that its new volume is #9 L#, how many moles of gas must be injected into the container to maintain a constant temperature and pressure?
1 Answer
Explanation:
To solve this problem, we can use the volumequantity relationship of gases, illustrated by Avogadro's law:
where

#n_1# and#n_2# are the initial and final quantities, in#"mol"# , of the gas, and 
#V_1# and#V_2# are the initial and final volumes of the gas, usually in#"L"#
Since we're trying to find how many moles of gas are needed to inject, we'll rearrange the equation to solve for
Our known quantities are

#n_1 = 3# #"mol"# 
#V_1 = 4# #"L"# 
#V_2 = 9# #"L"#
Plugging these values into the equation, we have
This is the total final volume; we were asked to find how many moles needed to be injected. To find this, we simply subtract the initial value from the final value:
Thus, to maintain a constant temperature and pressure, you must inject
If you follow the rules for significant figures, the answer is technically