March 26, 2017

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The Densities of Liquids and solids

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 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 - ,

    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= 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 - ,

    The correction for this(If anybody cares to look anymore) (I feel I have a responsibility to correct the error
    water mass = 78.19g - 23.94g-37.34g=
    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 - ,

    mass = 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 - ,

    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 - ,

    Ya, 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 - ,

    Yes 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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