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February 28, 2015

February 28, 2015

Posted by **Sara** on Wednesday, August 22, 2007 at 5:30pm.

O.k. so here is my problem. I will give you the whole problem just incase my mistake is somewhere else, but the volume for the metal and the density for the metal in the end seem to be wrong.

(Density of unknown liquid)

Mass of empty flask plus stopper 37.34g. Mass of stoppered flask plus water 63.67g. Mass of stoppered flask plus liquid 52.01. Mass of water (that I calculated) 26.33. Volume of flask(density of H2O at 25 degrees C, 0.9970 g/cm^3 (this was given) I calculated 37.45.

Mass of Liquuid 14.67. Density of liquid 14.72.

This is were my problem arises but I give you the above because the weight of the flask is the same...and I used that density.

(Density of unknwn metal)

Mass of stoppered flask plus metal 61.28. Mass of stoppered flask plus metal plus water 78.19. Mass of metal (according to my calculation) 23.94. Mass of water (also according to me) 16.91 and the volume of the water I calculated is 16.96. For the Volume of the metal I got 24.01 and for the density of the metal I got 0.991 g/cm^3....this seems odd, since the water and the metal would have the same density...so I figure I must be doing something wrong. I am really not sure what numbers to use to figure out the volume and density of the metal.

Please Help! I know this seems long, I just don't know were my mistake is.

- Chemistry -
**~christina~**, Wednesday, August 22, 2007 at 6:02pmD=M/V

Just my calculations..

empty flask + stopper= 37.34g

flask + stopper + water= 63.67g

water= 63.67g - 37.34g= 26.33g

D of water = 0.9970g/cm^3

V of water = M/D

V water= 26.40cm^3

flask + stopper + liquid = 52.01g

liquid= 52.01g- 37.34g= 14.67g

V same as water so...26.40cm^3

then to get D for unknown liquid

D=M/V

D= 14.67g/26.40cm^3 = 0.5556g/cm^3

Unknown Metal D

(have to find the volume)

stoppered flask + metal = 61.28g

stoppered flask empty (from before)= 37.34g

metal mass = 61.28g- 37.34g = 23.94g

Stoppered flask + water= 78.19g

water mass = (78.19g + 23.94g)-37.34g= 67.79g

Vol of water = Mass/Density

67.79g/(0.9970g/cm^3)= 67.99cm^3

Orig Vol- new Vol= 67.99cm^3-26.40cm^3= 41.59 cm^3 (vol of metal)

D of metal= Mass/Vol

23.94g/41.59cm^3= _________g/cm^3?

Hint: it's not the same =D

- Chemistry -
**~christina~**, Wednesday, August 22, 2007 at 8:00pmThe correction for this(If anybody cares to look anymore) (I feel I have a responsibility to correct the error

=()

So...

_______________________________________

water mass = 78.19g - 23.94g-37.34g=

16.91g

Vol of water = Mass/Density

16.91g/(0.9970g/cm^3)= 16.96cm^3

Orig Vol- new Vol= 26.40cm^3 -16.96cm^3= 9.44cm^3 (vol of metal)

D of metal= Mass/Vol

23.94g/9.44cm^3= 2.54g/cm^3?

I checked twice this time so it SHOULD be correct.

- Chemistry -
- Chemistry -
**DrBob222**, Wednesday, August 22, 2007 at 6:03pmmass = volume x density

volume = mass/density

volume of flask = 26.33/0.9970 = 26.41 cc or therebouts, not 37.45.

I didn't go through the remainder except that the mass of liquid is correct at 14.67.

Repost if this doesn't clear it up for you.

- Chemistry -
**DrBob222**, Wednesday, August 22, 2007 at 6:31pm**water mass = (78.19g + 23.94g)-37.34g= 67.79g**

Vol of water = Mass/Density

67.79g/(0.9970g/cm^3)= 67.99cm^3

I'm not sure I buy this part.

mass flask + metal + H2O = 78.19

mass flask + metal = 61.28

mass H2O = 78.19-61.28=16.91 g OR

flask + metal + H2O = 78.19

metal = 23.94

flask = 37.34

H2O = 78.19-23.94-37.34 = 16.91 g.

I think the mistake is ADDING the 23.94.

Check my thinking.

- Chemistry -
**Sara**, Wednesday, August 22, 2007 at 6:59pmYa, I noticed that too...I reposted what I did clearer, so please look at that version. I wrote down everything I did and were my problem is.

Thanks for the help!

- Chemistry -
- Chemistry -
**~christina~**, Wednesday, August 22, 2007 at 7:09pmYes Now looking at that again...

it should be subtraction.

Thanks for catching that Dr.Bob =D

(I should check twice next time)

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