Look at this equation: 2 H2 + O2 --> 2 H2O. Why isn't there any coefficient in front of oxygen? HELP!! A. A one is assumed when no coefficient is present.

B. There is an unlimited amount of oxygen

C. The 2 after the oxygen is all that is needed

D. All of these

...

Step-by-step explanation:

Explanation:

H

2

+

O

2

→

H

2

O

Notice the imbalance of atoms. On the left side, the reactant side, there are  

2

hydrogen atoms and  

2

oxygen atoms. On the right side, the product side, there are  

2

hydrogen atoms and only  

1

oxygen atom.

An important thing to remember when balancing equations is that the molecules themselves may not be changed—only their coefficients can. For example, we can change  

H

2

O

to  

3

H

2

O

but we can't go from  

H

2

O

to  

H

3

O

.

In order to deal with the original imbalance, the  

2

oxygens on the left and  

1

on the right, we can change the coefficient of the  

H

2

O

molecule from  

1

to  

2

.

H

2

+

O

2

→

2

H

2

O

Now we have the same amount of oxygens on each side,  

2

, but we have an unequal amount of hydrogen—there are  

2

on the left and  

4

on the right. We should achieve the least common multiple of the existing numbers, which is  

4

. We can make the  

H

2

on the left have a coefficient of  

2

, giving us the  

4

hydrogens that we need on that side of the equation, to match the  

4

on the right.

2

H

2

+

O

2

→

2

H

2

O