Dilution and Molarity Questions

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Jada Brown 2H
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Joined: Sat Aug 17, 2019 12:15 am

Dilution and Molarity Questions

Postby Jada Brown 2H » Tue Oct 01, 2019 8:25 pm

Whenever I first look at the more complex dilution questions, I tend to feel lost and not sure where to start. Does anyone have any tips as to where to start when you first look at these types of questions? Once I figure out how to start them I am usually fine.
Thank you!

Prasanna Padmanabham 4I
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Joined: Thu Jul 25, 2019 12:17 am

Re: Dilution and Molarity Questions

Postby Prasanna Padmanabham 4I » Tue Oct 01, 2019 8:30 pm

Most dilution question, however wordy (or confusing the textbook might try to make it sound) they might be, come down to the M1 * V1 = M2 * V2 formula. I would try to make a list of the information given and then maybe what you don't know (which is usually just one variable) and then solve the equation.

Brooke Yasuda 2J
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Joined: Sat Jul 20, 2019 12:17 am

Re: Dilution and Molarity Questions

Postby Brooke Yasuda 2J » Tue Oct 01, 2019 10:08 pm

When you begin with a dilution or molarity problem, first, just remember that molarity is the total moles of some solute (mol) divided by the total volume of a solvent (L). So with all of the given information, if you have something in grams I would begin with converting it to moles, and then carefully reading the question to figure out what information you have, and what information is needed. Make sure that you are also in the correct units.

Ying Yan 1F
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Joined: Fri Aug 02, 2019 12:16 am

Re: Dilution and Molarity Questions

Postby Ying Yan 1F » Tue Oct 01, 2019 10:17 pm

Personally, the dilution/molarity problems that confuses me are ones with more than two compounds, and in those cases, the key to solving the problem is to find the ratios of those ions/compouds in relation tto either the other ions/elements.

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Joined: Sat Sep 07, 2019 12:19 am

Re: Dilution and Molarity Questions

Postby Chantel_2I » Wed Oct 02, 2019 11:01 am

I think the problem becomes clearer once you can see the molar ratios between the given molecule and the one being asked for. After you can relate the two, it's easier to use the information you have in an effective way.

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Joined: Sat Sep 07, 2019 12:19 am

Re: Dilution and Molarity Questions

Postby Mariepahos4D » Wed Oct 02, 2019 11:04 am

Generally, the best way to start is to carefully read the problem and write out the given measurements to clearly see what you are looking for. I usually start by solving the molarity and then go from there. With this information I can then see if it is a problem where I use M=mols/L or M1V1=M2V2

Maika Ngoie 1B
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Joined: Fri Aug 02, 2019 12:16 am

Re: Dilution and Molarity Questions

Postby Maika Ngoie 1B » Wed Oct 02, 2019 11:07 am

Sometimes molarity and dilution problems can seem a bit wordy and overwhelming. For me, I always begin by writing down the number values that they give me and determining which are useful depending on what part of the problem I am at. That was I can interpret the real meaning of all the information I'm being given.

Jillian C 4C
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Re: Dilution and Molarity Questions

Postby Jillian C 4C » Wed Oct 02, 2019 11:39 am

In answering these types of problems, I write down the values that are given to me and think about the formula I can use, which is usually M1xV1=M2xV2. I figure out the desired molarity and volume as well as the initial molarity and volume, then plug those values into the formula.

John Arambulo 1I
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Joined: Sat Jul 20, 2019 12:15 am

Re: Dilution and Molarity Questions

Postby John Arambulo 1I » Wed Oct 02, 2019 12:13 pm

When doing molarity and dilution problems, it is essential to know which of the given volumes and concentrations correspond with each other. For example, 50mL of a 0.5M sol of A, and you want to calculate the concentration of 250mL of sol B that would neutralize sol A. To solve this, I make sure I know that 50mL corresponds to 0.5M sol A and have 250mL for sol B by underlining or rewriting them in my work. Then I would solve for the concentration of sol B.
1. Convert solution A into moles by converting 50mL to 0.05L and multiplying it by the concentration of 0.5M where L would cancel out and you have 0.025 moles of A.
2. When finding the concentration or number of moles in a solution that is neutralized, it is always important to think of moles A=moles B, like how in the Molarity lecture and modules, .
3. Applying this to the problem, you know that the moles of sol B must be 0.025.
4. To find the concentration, you would divide the moles of B by the volume of sol B given in the problem. So you would get 0.025 mol B/.250L = 0.1 M solution B

Overall, just make sure you know which values that are given correspond to each other, and what value you are solving for. Then you can continue by going through the formula with the values you have and solving for your final answer.

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