GChem Question

[Kremlar]

Hey all, I have a pretty simple Gen Chem question that has been killing me...

A flask weighs 95g when empty, when filled with 200mL of a certain liquid, the weight is 328g. What volume in mL would 1000g of the liquid occupy?

Can someone explain to me how and what formula you would use to solve this? I know the liquid weighs 328-95= 233g
For some reason, im dying to use the formula D=M/V ---> V= M/D
Since you can find the density of the unknow liquid = g/mL and you have a mass that you need to know the volume of.. answer says otherwise...
Any ideas??
Much appreciated...

---

Members don't see this ad.

 

[tinman831]

Hey all, I have a pretty simple Gen Chem question that has been killing me...

A flask weighs 95g when empty, when filled with 200mL of a certain liquid, the weight is 328g. What volume in mL would 1000g of the liquid occupy?

Can someone explain to me how and what formula you would use to solve this? I know the liquid weighs 328-95= 233g
For some reason, im dying to use the formula D=M/V ---> V= M/D
Since you can find the density of the unknow liquid = g/mL and you have a mass that you need to know the volume of.. answer says otherwise...
Any ideas??
Much appreciated...

you have 233g per 200 mL and you want to find the volume of 1000g
so take (200mL / 233g) * 1000g

or 200mL / 233g = X mL / 1000g and solve for X

 

[786mine]

6000ml

sol:

mass of 200ml is 33g.
you can fit 30 samples of 33g, to make almost 1000g
meaning, 30 times 200 = total volume which is 6000ml.

 

[tinman831]

6000ml

sol:

mass of 200ml is 33g.
you can fit 30 samples of 33g, to make almost 1000g
meaning, 30 times 200 = total volume which is 6000ml.

mass is 233g... not 33g 🙂

 

[Kremlar]

you have 233g per 200 mL and you want to find the volume of 1000g
so take (200mL / 233g) * 1000g

or 200mL / 233g = X mL / 1000g and solve for X

Im with you Tinman, I got something similar.. I got 233g/200mL=1000g/XmL Rearrange to solve for X...
The answer the book gives is [200x1000]/328-95 (its a setup problem) thats why I wanted to know what formula this would fall under and how to use it properly on this equation.
It still doesnt make sense to me, even with the answer...

 

[joonkimdds]

Im with you Tinman, I got something similar.. I got 233g/200mL=1000g/XmL Rearrange to solve for X...
The answer the book gives is [200x1000]/328-95 (its a setup problem) thats why I wanted to know what formula this would fall under and how to use it properly on this equation.
It still doesnt make sense to me, even with the answer...

ah...i don't remember any of these... 🙁 how did i get an A in both sessions of GCHEM, lol....

 

[SMC2UCLA2_]

Im with you Tinman, I got something similar.. I got 233g/200mL=1000g/XmL Rearrange to solve for X...
The answer the book gives is [200x1000]/328-95 (its a setup problem) thats why I wanted to know what formula this would fall under and how to use it properly on this equation.
It still doesnt make sense to me, even with the answer...

The answer the book gives is the same answer Tinman gave you. Like Tinman stated, there is two ways to look at this, either simplify units or cross multiply.

If you simplify units, this is how I go about it: The question tells you that you want the volume of 1000 g of the liquid, so you should realize your units need to cancel and leave you with volume. D= m/v so flip this around to 1/D (simply v/m) and multiply by the 1000 g to eliminate the denominator and now your final answer will be volume since units of gram will cancel ((v/m) * m => v). Heres the math

d= m/v= (328g-95g)/200ml
1/D = v/m => 200ml/(328g-95g)
(v/m) * m = v ==> 200ml/(328g-95g) * 1000 g <--simplify this into (200ml*1000g)/(328g-95g)

Let me know if that makes sense to you.

 

[Kremlar]

The answer the book gives is the same answer Tinman gave you. Like Tinman stated, there is two ways to look at this, either simplify units or cross multiply.

If you simplify units, this is how I go about it: The question tells you that you want the volume of 1000 g of the liquid, so you should realize your units need to cancel and leave you with volume. D= m/v so flip this around to 1/D (simply v/m) and multiply by the 1000 g to eliminate the denominator and now your final answer will be volume since units of gram will cancel ((v/m) * m => v). Heres the math

d= m/v= (328g-95g)/200ml
1/D = v/m => 200ml/(328g-95g)
(v/m) * m = v ==> 200ml/(328g-95g) * 1000 g <--simplify this into (200ml*1000g)/(328g-95g)

I think I got it somewhat?, thats why I hate setup problems more than anything... It's easiter to solve the thing and find an answer than find how they decided to simplify an answer... My question is, why did you flip the fraction to solve for 1/d..the way I had it set up, the units still cancel out and your left with mL as the final unit..just it was upside down from what they had...I couldnt figure out why they put the 1000g on top.. thanks
Phil

 

[SMC2UCLA2_]

The answer the book gives is the same answer Tinman gave you. Like Tinman stated, there is two ways to look at this, either simplify units or cross multiply.

If you simplify units, this is how I go about it: The question tells you that you want the volume of 1000 g of the liquid, so you should realize your units need to cancel and leave you with volume. D= m/v so flip this around to 1/D (simply v/m) and multiply by the 1000 g to eliminate the denominator and now your final answer will be volume since units of gram will cancel ((v/m) * m => v). Heres the math

d= m/v= (328g-95g)/200ml
1/D = v/m => 200ml/(328g-95g)
(v/m) * m = v ==> 200ml/(328g-95g) * 1000 g <--simplify this into (200ml*1000g)/(328g-95g)

I think I got it somewhat?, thats why I hate setup problems more than anything... It's easiter to solve the thing and find an answer than find how they decided to simplify an answer... My question is, why did you flip the fraction to solve for 1/d..the way I had it set up, the units still cancel out and your left with mL as the final unit..just it was upside down from what they had...I couldnt figure out why they put the 1000g on top.. thanks
Phil

OK so lets do it like you had it because it will work fine as well. You say you are tempted to convert D= m/v into v=m/D.

First things first. Find the density from the given information:
D = m/v = (328g-95g)/200 ml

Now the problem asks what volume will 1000 grams of sample occupy.
So, convert D= m/v to v= m/D and solve for v
use m= 1000g
V= 1000g/D where D=(328g-95g)/200 ml
V= 1000g/[(328g-95g)/200 ml]

dividing by a fraction is the same as multiplying by the reciprocal so:
V= 1000g * [200 ml/(328g-95g)] = (1000g * 200ml)/(328g-95g)

grams cancel and you are left with ml. If i had to speculate, I would say that you are probably canceling the units correctly but you are not flipping the bottom fraction

 

[n2o*]

Lol. this problem is actually much simpler than people are making it out to be.

So what we've established that 20ml of the liquid weighs 233 grams (95g for the empty container and 328 when we add 20ml of water gives us 328-95 g of liquid)

All we need to do is to set up a proportion:

20ml of liquid/X ml liquid = 233g/ Xgrams When you solve for X you get 85.83ml lof liquid.

Hope this helps 🙂

 

[Kremlar]

OK so lets do it like you had it because it will work fine as well. You say you are tempted to convert D= m/v into v=m/D.

First things first. Find the density from the given information:
D = m/v = (328g-95g)/200 ml

Now the problem asks what volume will 1000 grams of sample occupy.
So, convert D= m/v to v= m/D and solve for v
use m= 1000g
V= 1000g/D where D=(328g-95g)/200 ml
V= 1000g/[(328g-95g)/200 ml]

dividing by a fraction is the same as multiplying by the reciprocal so:
V= 1000g * [200 ml/(328g-95g)] = (1000g * 200ml)/(328g-95g)

grams cancel and you are left with ml. If i had to speculate, I would say that you are probably canceling the units correctly but you are not flipping the bottom fraction

Thanks SMC2 for the explanation... I couldnt figure out how they set it up..
I got it now.... Now lets hope I get it on my test too....lol...

 

[tinman831]

you should take a closer look at the stoichiometry section in your chemistry book. it covers how to convert from one set of units to another using a set of given relationships. not all problems will be so clear cut, such as using the d = m/v formula to solve this equation. for example, if a person loses five pounds in 2 minutes. how many pounds will a person lose in 10 minutes? there's no specific formula to use. you have to solve the problem using stoichiometry.

 

[Kremlar]

you should take a closer look at the stoichiometry section in your chemistry book. it covers how to convert from one set of units to another using a set of given relationships. not all problems will be so clear cut, such as using the d = m/v formula to solve this equation. for example, if a person loses five pounds in 2 minutes. how many pounds will a person lose in 10 minutes? there's no specific formula to use. you have to solve the problem using stoichiometry.

Hey Tinman, thanks for the advice, I read over the chapter in my old textbook. But it didnt help me solve that problem. I couldnt figure out the setup. Are there any other types of problems you can think of like you mentioned that I should be concentrating on? Thanks for the advice...