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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: tarsis20 on May 07, 2008, 02:19:43 PM

Title: Unit Conversions (Dimensional Analysis)
Post by: tarsis20 on May 07, 2008, 02:19:43 PM
Here is the problem:

A fish tank is 20.0 inches long, 20.0 inches deep, and 10.0 inches high. What is the maximum volume of water, in liters that the fish tank can hold?

Tip: V= M/D

I don't know how to get the mass and the volume since the problem doesn't give it. It just gives the dimension of the fish tank. I know that this dimensions must be the clue but I don't know how to use them in order to resolve the problem.

I tried to change the dimensions from inches to liters but I doesn't help me too much... or maybe I did them wrong... I don't know.

I hope someone can tell me how to approach the problem. I don't need exact answer. I just want a clarification and an explanation of how to do these type of exercises ???.

Thanks all
Title: Re: Unit Conversions (Dimensional Analysis)
Post by: Kuahji on May 07, 2008, 02:25:16 PM
Just multiply the length, width, & height together.  That will give you the volume of the tank. 

Once you find this, the best thing to do, is to convert the in3 to cm3 & from there to mL.  1 cm3=1 mL

You can't really get the mass from the information given, so don't worry about that, just use the above formula for volume. 
Title: Re: Unit Conversions (Dimensional Analysis)
Post by: Kuahji on May 07, 2008, 02:33:55 PM
Or rather, come to think of it, an easier approach is to convert the inches to cm first.  Then multiply the length, width, and height together.  This will save time & be less confusing.  Because then the cm3=mL.

Sorry for the confusion.  Hope that makes sense.   ;D

Here is an example.  Suppose your tank as 2.54 in wide, 2.54 in high, 2.54 in long.

There are 2.54 centimeters in an inch.  So
2.54 in * 2.54cm / 2.54in = 1cm

1 cm * 1 cm * 1cm = 1 cm3

1 cm3 * 1 mL / 1cm3 = 1 mL

1 mL * 1 L / 1000 mL = .001 L
Title: Re: Unit Conversions (Dimensional Analysis)
Post by: tarsis20 on May 07, 2008, 02:40:01 PM
Thanks it really helps!!! I don't know why I stick with the density formula and tried to adjust it instead of using the volume one but anyways thank you for your #elp!!!!!!   ;)
Title: Re: Unit Conversions (Dimensional Analysis)
Post by: Borek on May 07, 2008, 04:35:04 PM
It is a small tank ;)