orion Posted January 30, 2010 Share Posted January 30, 2010 Hey guys. This is mrs.orion. Anyone here able to explain Molarity as it relates to density??? I'm completely stuck on a homework problem (for some reason the steps to the math aren't making sense to me). Here's the problem : A solution is prepared by dissolving 22.4 g NaOH in 124.0 g of water. The NaOH solution has a density of 1.15 g/mL. a) What is the % (m/m) concentration of the NaOH solution? 15.3% (This one I got!) b) What is the total volume (mL) of the solution? This is where I'm having an issue.... c) What is the molarity ( M ) of the solution? This one I'll have no trouble answering once I get over the part b block. I'm also assuming I'll need the molar mass at some point (which is 39.998 g/mole - I can round sig figs later). Quote Link to comment Share on other sites More sharing options...
moovinfast Posted January 30, 2010 Share Posted January 30, 2010 For b, use dimensional analysis. You have all the information you need in the first line of the problem. You need to go from grams to mL and you will use the density units g/mL to convert between the two. You know that there are 1.15g per mL of solution (given by the density), you have a total of 146.4g of solution. 1.15 g/1 mL = 146.6 g/x mL Just solve for x and you'll have your answer x mL = 146.6 g * 1 mL/1.15 g Quote Link to comment Share on other sites More sharing options...
orion Posted January 30, 2010 Author Share Posted January 30, 2010 Thank you! For some reason I just wasn't getting that I needed to divide by the density...lol Quote Link to comment Share on other sites More sharing options...
Algae Posted January 31, 2010 Share Posted January 31, 2010 What! You molarity what? NAo3xy+/w2 X 3BS -34.556 = ADD ???????? Ahh... Now I realize why I majored in "Social" Science and Fine Art. Hey guys. This is mrs.orion. Anyone here able to explain Molarity as it relates to density??? I'm completely stuck on a homework problem (for some reason the steps to the math aren't making sense to me). Here's the problem : A solution is prepared by dissolving 22.4 g NaOH in 124.0 g of water. The NaOH solution has a density of 1.15 g/mL. a) What is the % (m/m) concentration of the NaOH solution? 15.3% (This one I got!) b) What is the total volume (mL) of the solution? This is where I'm having an issue.... c) What is the molarity ( M ) of the solution? This one I'll have no trouble answering once I get over the part b block. I'm also assuming I'll need the molar mass at some point (which is 39.998 g/mole - I can round sig figs later). Quote Link to comment Share on other sites More sharing options...
fishmanmike01 Posted January 31, 2010 Share Posted January 31, 2010 A solution is prepared by dissolving 22.4 g NaOH in 124.0 g of water. The NaOH solution has a density of 1.15 g/mL. a) What is the % (m/m) concentration of the NaOH solution? 15.3% (This one I got!) b) What is the total volume (mL) of the solution? This is where I'm having an issue.... c) What is the molarity ( M ) of the solution? This one I'll have no trouble answering once I get over the part b block. (scratch) ??????? Huh ???????(nutty) Now i really feel stupid. Quote Link to comment Share on other sites More sharing options...
orion Posted January 31, 2010 Author Share Posted January 31, 2010 hehehe This is what happens when 30 year olds go back to school. hehehe I get the reactions and stuff, but when they toss in a bunch of math, it seems I'm completely lost. I did get the answer right on the homework though, so that's awesome...midterm this week so let's hope I can do as well on that as I've been doing in the rest of the class! I *wish* I wanted to major in social sciences and fine art...lol Next term starts my anatomy & physiology series, statistics, and psychology. Psychology is going to be a breeze...it's the other two I'm going to stress about. Quote Link to comment Share on other sites More sharing options...
racefan Posted January 31, 2010 Share Posted January 31, 2010 (scratch) ??????? Huh ???????(nutty) Now i really feel stupid. Don't worry I didn't understand one word of that:D Quote Link to comment Share on other sites More sharing options...
Rapture Rabbit Posted January 31, 2010 Share Posted January 31, 2010 Don't worry I didn't understand one word of that:D Thank god. I thought I was the only one... I went to art school. (laugh) Quote Link to comment Share on other sites More sharing options...
moovinfast Posted February 1, 2010 Share Posted February 1, 2010 I dont get it either. Thank goodness for my wife. Quote Link to comment Share on other sites More sharing options...
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