Need help with these 2 GC questions on 2009 ADA Test

[bigndog525]

41. 492 g kerosine are required to fill container. Density of kerosine is .82 g/ml-1. At the same temp, density of mercury is 13.5 g/ml-1. What mass of mercury is necessary to fill container?

63. What is the best piece of lab equipment to measure 12.44 mL of a solution. The Destroyer says it is the pipet and I put that but got it wrong!

erlenmyer flask
beaker
pipet
buret
weighting bottle

What's the answer and why?

---

Members don't see this ad.

 

[radmazindds]

I'd choose a buret. If you remember from lab, it can fit up to 50 mL of sol'n and it's gradated every 1/10 mL (or at least ours were). Pipettes are way too small! You can probably measure out 5mL in those things plus there are no gradations (you have to count drops and approximate). These are appropriate only for very small amounts. google image those two and you'll see the difference.

63. What is the best piece of lab equipment to measure 12 mL of a solution. The Destroyer says it is the pipet and I put that but got it wrong!

erlenmyer flask
beaker
pipet
buret
weighting bottle

What's the answer and why?

 

[bigndog525]

I'd choose a buret. If you remember from lab, it can fit up to 50 mL of sol'n and it's gradated every 1/10 mL (or at least ours were). Pipettes are way too small! You can probably measure out 5mL in those things plus there are no gradations (you have to count drops and approximate). These are appropriate only for very small amounts. google image those two and you'll see the difference.

thats an eye dropper.. I think it is referring to the pipet that is used in a research lab.... or for PCR...

http://www.esuppliersindia.com/fine...d-handling-product-pr171808-sCATALOG-swf.html

 

[radmazindds]

That MICROpipette measures in microliters.

thats an eye dropper.. I think it is referring to the pipet that is used in a research lab.... or for PCR...

http://www.esuppliersindia.com/fine...d-handling-product-pr171808-sCATALOG-swf.html

 

[PooyaH]

The key word for pipette is "transfer" of solutions. Buret gives you more accurate measurements than a pipette.

 

[needzmoar]

41. 492 g kerosine are required to fill container. Density of kerosine is .82 g/ml-1. At the same temp, density of mercury is 13.5 g/ml-1. What mass of mercury is necessary to fill container?

63. What is the best piece of lab equipment to measure 12 mL of a solution. The Destroyer says it is the pipet and I put that but got it wrong!

erlenmyer flask
beaker
pipet
buret
weighting bottle

What's the answer and why?

#41
You're asked to figure out the mass required to fill a fixed volume. The given density enables you to relate the mass to the volume.

492g (1mL/.82g) = volume that kerosene occupies = volume of container = 600mL

Now we use the density of Mercury to figure out the mass required to occupy 600mL

600mL(13.5g/1mL) = 8100g

#63 see the above posts

 

[rocky90]

Do you get such numbers in the question as in 41 to calculate. That would take time..this is freaking me out now.

 

[LetsGo2DSchool]

Look for the key words "transfer" or "titration". If transfer, then it's a pipette. If titration, then it's a buret. If it doesn't say ****, then it's a 50/50 guess.

 

[bigndog525]

lol ok... but can anyone solve that other problem please?

 

[PooyaH]

lol ok... but can anyone solve that other problem please?

Needsmoar already did!

First you get the volume of the container: Since .82g/ml = 421g/ml, then ml = 421/.82 = 600ml

And since you're filling up the same container and you know the volume is 600ml: 13.5g/ml = g/600ml, so g of Mercury = (13.5)(600) = 8100g

 

[Dental2000]

Other problem was solved...just scroll up

Here's what you do in a nutshell
find The volume using mass and density of kerosine.

Once you get that its gonna be the same for mercury since your using the same container ....

use that volume and density of mercury to find mass of mercury...