[thePrince]

Hi, I'm new to chemistry and have found problems all ready. Please help locate my errors and explain concepts.

(1) A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance B and gas C. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. What can we say about whether solids A and B and the gas C are elements or compounds?

I was given the answer but I don't understand it.

(2) 5.0 x 10^-9 m to pm

5.0 x 10 ^-9 m (10^-12 pm/ 1 m)
= 5 x 10^-21 pm

(3) 3.5 x 10^-2 mm to um
(1 um/ 10^-6 m)(1 m/.001 mm) (3.5 x 10 ^-2 mm)
=35000000

(4) Gold can be hammered into extremely thin sheets called gold leaf. If a 200 mg piece of gold (density = 19.32 g/cm^3) is hammered into a sheet measuring 2.4 x 1.0 ft, what is the average thickness of the sheet in meters? How might the thickness be expressed without expo. notation, using an appropriate metric prefix?

I'm not even sure where to begin.

---Any help would be great. Thanks in advance.---

[arit]

(1) A solid white substance A is heated strongly in the absence of air. It decomposes to form a new white substance B and gas C. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. What can we say about whether solids A and B and the gas C are elements or compounds?

An element contains only atoms whose nuclei have the same amount of protons. (You can't split an element into another elements)
A compound is a substance that is composed of atoms of two or more kinds of elements.

Substance A clearly breaks up into another substances.
What do you get when you burn carbon in excess oxygen? An element or a compound?

Substance B is a harder one to guess, there's not much said about it.