# Mass-Volume Question

1. Oct 4, 2008

### someone21

A uranium alloy has density of 18.75 g/cm3. Find the volume if occupied
by a critical mass of 49 kg of this alloy? The critical mass itself can be decreased to 16
kg if the alloy is surrounded by a layer of natural uranium ( neutron reflector). What is the volume of the smaller mass?

I am sorry but I have no idea how to do this question, I just don't get how to start , like should i use moles or possibly nuclear equations. No idea

Lastly, more importantly any good sites to teach how to draw Lewis structure

2. Oct 4, 2008

### Staff: Mentor

You have mass, you have density, just use these number to calculate volume. That's all.

3. Oct 4, 2008

### someone21

Thanks but then what is all the decreased mass and all those

And they are asking the 'smaller' mass

4. Oct 4, 2008

### Staff: Mentor

You have two masses given - 49 kg and 16 kg. One is larger, one is smaller. There is nothing more to the question, everything else is just to make the question more interesting (or more confusing if you like).

5. Oct 4, 2008

### someone21

So the answer is 16000 g /18.75g

And what will the unit for volume be

6. Oct 5, 2008

### Staff: Mentor

$$\frac {16000 g} { 18.75 \frac {g} {mL}}$$

Units follow from that.

7. Oct 7, 2008

### someone21

Thanks for answering that but I had one more question as in my first post

Lastly, more importantly any good sites to teach how to draw Lewis structure

I know that there are many sites from google but i somehow dont find it easy to understand thereby any other good sites