Question #9be80
1 Answer
You have
Explanation:
The idea here is that you need to use the number of moles of potassium that you get per mole of potassium sulfate,
If you look at the formula unit of potassium sulfate, you'll notice that it contains
- two potassium atoms
#-># you get that from the#2# subscript; - one sulfur atom
- four oxygen atoms
#-># you get that from the#4# subscript.
This means that 1 mole of potassium sulfate will contain 2 moles of potassium, 1 mole of sulfur, and 4 moles of oxygen.
In your case, you have 0.400 moles of ptoassium sulfate, which means that you have
#0.400color(red)(cancel(color(black)("moles K"_2"SO"_4))) * "2 moles K"/(1color(red)(cancel(color(black)("moles K"_2"SO"_4)))) = "0.800 moles K"#
Now just use potassium molar mass to get the number of grams that would contain this many moles
#0.800color(red)(cancel(color(black)("moles K"))) * "39.0983 g K"/(1color(red)(cancel(color(black)("mole K")))) = color(green)("31.3 g K")#
Here's a list of videos on percent composition, check them out!
http://socratic.org/chemistry/the-mole-concept/percent-composition/videos
