Consider the reaction: 2 NO(g) + 5 H2(g) → 2 NH3(g) + 2 H2O(g)A reaction mixture initially contains 5 moles of NO and 10 moles of H2. Which set of amounts best represents the mixture after the reactants have reacted as completely as possible?

After the complete possible reaction of the mixture, 1 mole of NO has remained in the reaction mixture.

The balanced chemical equation for the reaction will be:

According to the reaction,

2 moles of NO requires 5 moles of Hydrogen.

The given moles of NO have been 5 moles. The hydrogen required has been:

2 moles NO = 5 moles hydrogen

5 moles NO = moles Hydrogen

5 moles NO = 12.5 moles Hydrogen.

The available hydrogen has been 10 moles. It has been insufficient to completely react with the NO. Thus hydrogen has been the limiting reactant.

The complete utilization of hydrogen requires:

5 moles hydrogen = 2 moles NO

10 moles hydrogen = moles NO

10 moles hydrogen = 4 moles NO.

The complete utilization of hydrogen requires 4  moles of NO. The available NO has been 5 moles. The remaining NO has been given as:

Remaining NO = Total - consumed

Remaining NO = 5 - 4

Remaining NO = 1 mole

After the complete possible reaction of the mixture, 1 mole of NO has remained in the reaction mixture.

For more information about the reactant that remained in reaction, refer to the link:

link

Explanation:

2 NO(g) + 5 H2(g) → 2 NH3(g) + 2 H2O(g)

From the reaction above, 2 moles of NO requires 5 moles of H2 to obtain 2 moles of NH3 and 2 moles of H2O

If all the 5 moles of NO was used, it would require;

2 moles of NO = 5 moles of H2

5 moles of NO = x

x = 12.5 moles of H2

However there is only 10 moles of H2. This makes it the limiting reactant.

When the 10 moles of H2 are used;

5 moles of H2 = 2 moles of NO

10 moles of H2 = x

x = 4 moles of NO

This means 4 moles of NO and 10 moles of H2 are used.

Only 1 mole of NO would remain.

neutrons are in the middle of the atom and the electrons, which are much smaller.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)