What is the molarity of a solution that contains 5 moles of solute in 2 liters of solution?

Answer 1

* First! Figure out what pyridine's formula is: C5H5N So, we know that each molecule of pyridine has 5 C, 5 H, and 1 N. The cool thing about the formula is it doesn't matter what the unit is, as long as the ratio between the C, H, and N remains the same, BUT, being that we're doing chemistry let's use moles. :) 5 moles of C + 5 moles of H + 1 mole of N -->1 mole of C5H5N This can be a weird concept, because you might think "how do you put in 11 moles of stuff and get only one mole of product"... but, just like baking, you put in 5 cups of sugar, 5 cups of flour, and 1 cup of butter, but get one really big cookie (didn't say it would be a good cookie). Well, you put in a few moles of this, a few moles of that...and you get a single mole of C5H5N. * After you figure out the chemical formula, calculate molecular mass: 5 moles of carbon = 5 x 12.011 grams per mole = 60.055 grams 5 moles of hyrdrogen = 5 x 1.008 grams per mole= 5.04 grams 1 mole of nitrogen = 1 x 14.007 grams per mole= 14.007 grams ADD: 60.055 + 5.04 + 14.007 = 79.102 grams per 1 mole of C5H5N * Convert solute to moles! Now, we've figured out that 1 mole of C5H5N has a mass of 79.102 grams....but, we're only putting 5 grams in the solution. How many moles is 5 grams if 1 mole is 79.102 grams? Calculate: 5 grams/ 79.102 grams = .063 moles * Convert to moles per liter (not moles to part of a liter)! So...we are adding .063 moles to .5 liters of solvent, but, molarity is always expressed in moles per liter, so we have to convert this: (.063 moles C5H5N/.5 liter) x 1 liter = .126 moles C5H5N So, if .063 moles of C5H5N dissolved in .5 liters gives a solution of the same concentration as 1.26 moles of C5H5N dissolved in 1 liter (note - we now have it in moles per liter!). As molarity is moles per liter...and adding 5 grams of pyridine (which is .063 moles) to .5 liters of solvent produces a solution of the same concentration (molarity) as dissolving 1.26 moles of solvent in 1 liter, we have produced a 1.26 molar solution.

Answer 2

2.5m