[lokobreed]

I need help with these questions they are concerning density.  This is general chemistry
. If you could help me with how to do these problems.

A rectangular block of lead has a mass of 175.3 g calculate the height of the block if the width is 2.25 cm and that length is 3.15 cm

An iron ore weighing 83.245 g was placed in a flask having a volume of 54.25 ml.  The flask with the iron ore was then filled with water and weighed.  The iron ore and water weighed 124.481 g.  The density of water is 0.9976 G/ml.  Calculate the density of the iron ore.

Thank you

[lokobreed]

For the first one I am completely lost.
For the iron ore when I take 124 0.481 g divided by 0.99726 G ML and subtract that from 70.530473 and come up with the answer of the density for the iron ore as 1.18?

[rabolisk]

Density is mass/volume. It relates mass of a substance to the volume of a substance. In other words, density tells you how much volume a given mass of substance will occupy. E.g. You can figure out how much volume 1 g of water occupies if you know it's density.

A formula for a volume of a solid is length x width x height (which you should know from geometry).

Where did you get 70.53 from?? You are not doing this right.

[lokobreed]

yes i feel lost right now ;/ and studying intensely.

ok, so for the block of lead if i found the volume of the block of lead to be 15.5 because the mass is 175.3 g and the density (from given in the problem) is 11.3 g/cm3 then the height would be 2.19 cm correct?

For the iron ore i got the 70.53 from dividing the weight of the ore be density of water... which i see is wrong completely. any tips on this ?

[rabolisk]

Correct.

You have iron ore with known mass but unknown volume and unknown density. You have water with known density but unknown mass and unknown volume. You HHS a flask whose volume is known.

In this problem, both mass and volume are additive. That is, mass(ore + water) = mass(ore) + mass(water). Same idea with volume. Once you figure out the role of volume(flask) you should be able to solve this.

[lokobreed]

thank you so much for the *delete me* I am still confused on this problem... I am thinkinh I need to find out the volume difference with the ore and without and then divide that to find the density of the ore?

If this is correcT?

[rabolisk]

Before you can find the density of ore, you need to find the volume of ore, which is volume of flask - volume of water. To find the volume of water, you need to use more information that is given in the problem.

[lokobreed]

Thanks again!

Ok I think I figured it out.

Density of ore = 83.245g/V of ore

Volume of flask - Volume of water is 54.25 (Volume of Flask) - 41.34 (Volume of Water)

I got the volume of water by doing setting the problem up as .9976 (density of water) = 41.236 (124.481 - 83.245)/ V
V = 41.34

So then the volume of flask - volume of water is 12.91 so the density of the ore is 83.245/12.91 = 6.448

[rabolisk]

That's right. Now can I get some mole snacks?? 

[lokobreed]

thank you so much!

Mole snacks given

[lokobreed]

Can anyone please help with this problem.
A container has a mass of 78.91 g when empty and 103.782 g one filled with water.  The density of water is 1.0000 g/cm3.  Calculate the volume of the container.  When filled with an unknown liquid, the container had a mass of 88.42 g.  Calculate the density of the unknown liquid.
I have attempted this problem but continue to become confused on how to set this up.

[rabolisk]

This is very similar to the one with the ore. One hint, if you were given a cup, and you filled it all the way with x volume of water, then what is the volume of the cup?

[lokobreed]

as you can tell chemistry is not my strong point but I am determined to learn it.

Ok well I would need to know the cups mass correct because V=M/D

So for this problem to caluclate the volume of the container would I take the Mass of the container with liquid minus the mass of the container with out the liquid - 103.72 - 78.91 and divide it by density of water 1.000 g/cm3?

and to find the density of the unkown liquid would I use the mass of the container and divide it by the volume found above?

[rabolisk]

Yes on the volume of the container, but no on the second one. To find density of x, you need mass of x and volume of x. Mass of the container is not the same thing as mass of the unknown liquid.

[lokobreed]

im giving you more mole snacks! lol

Ok so to find the volume i would do with liquid - w/o liquid divided by the density of liquid? correct?
Since Mass of X is given in the problem as 88.42, how do i find the volume of X ?

Thanks again