Answer : The reagent present in excess and remains unreacted is, 
Solution : Given,
Moles of
= 3.00 mole
Moles of
= 2.00 mole
Excess reagent : It is defined as the reactants not completely used up in the reaction.
Limiting reagent : It is defined as the reactants completely used up in the reaction.
Now we have to calculate the limiting and excess reagent.
The balanced chemical reaction is,

From the balanced reaction we conclude that
As, 2 moles of
react with 1 mole of 
So, 3.00 moles of
react with
moles of 
From this we conclude that,
is an excess reagent because the given moles are greater than the required moles and
is a limiting reagent and it limits the formation of product.
Hence, the reagent present in excess and remains unreacted is, 
A burning fossil fuels that produces energy
It's a physical property because it doesn't change the element of the metal.
does this make sense?
Answer:
Rate expression has been given below
Explanation:
According to the given equation, 1 molecule of A reacts with 1 molecule of B and produces 2 molecules of B at a time.
So, rate of disappearance of both A and B are one half of rate of appearance of B
Hence rate expression can be represented as:
![Rate=\frac{-\Delta [A]}{\Delta t}=\frac{-\Delta [B]}{\Delta t}=\frac{1}{2}\frac{\Delta [C]}{\Delta t}](https://tex.z-dn.net/?f=Rate%3D%5Cfrac%7B-%5CDelta%20%5BA%5D%7D%7B%5CDelta%20t%7D%3D%5Cfrac%7B-%5CDelta%20%5BB%5D%7D%7B%5CDelta%20t%7D%3D%5Cfrac%7B1%7D%7B2%7D%5Cfrac%7B%5CDelta%20%5BC%5D%7D%7B%5CDelta%20t%7D)
where
is rate of disappearance of A,
is rate of disappearance of B and
rate of appearance of C