<span>By using the mole ratio, we can determine that 2 moles of NH3 are made when 3 moles of hydrogen gas are present. The numbers in front of the chemicals tell us the relative amounts consumed and produced. Since there is a 3 in front of H2 and a 2 in front of NH3, this tells us that for every 3 moles of H2 gas used, 2 moles of NH3 are made.</span>
To answer this question, you need to know the concept of half-life, which is how a radioactive material decreases in mass over time.
The half life of U-235 is 703.8 million years. The first part of this problem is to find the scale factor. To do this, divide the time that has past by the half life, like this:

Now, take this scale factor and multiply it by the current mass, like this:

This number is what you add to the current mass to get the original mass. That is because the scale factor showed us that it was just over one half life. Since after one half life, the mass is cut in half, and this is over one half life, when we add to the original it will be a little over double. This equation illustrates the final addition:

I hope this helped you. Fell free to ask any further questions.
Answer:
Because it went through a chemical change which changes its atomic form
The food chain always begins with a sun without it there would be no food chain... hope this helped!
The answer is
<span>2PbS(s) + 3O2(g) = 2PbO(s) + 2SO2(g)
Your answer is not yet balanced because you have 3 oxygen atoms. it should be balanced by multiplying both side by 2 such as the balanced equation I made. To check it, I will explain why your answer is not yet balanced.
check: (from your equation)
</span> 1-Pb-1
1-S-1
2 -O-3
the difference between the reactant and the product of Oxygen will prove that it is not yet balanced.
If you use 2PbS(s) + 3O2(g) = 2PbO(s) + 2SO2(g), to check it:
2-Pb-2
2-S-2
6 -O-6
then this is now balance