If 2.0 moles of a and 5.0 moles of b react according to the hypothetical reaction below, how many moles of the excess reactant will be left over at the end of the reaction?

a + 2b → ab2 (d, right? )

0.50 mol a left over

0.50 mol b left over

1.0 mol a left over

1.0 mol b left over

To determine the amount of excess reactant left, we need to first identify which is the limiting and the excess reactant. We do as follows:

A + 2B → AB2

2 mol A ( 2 mol B / 1 mol A) = 4 mol B needed to be consumed completely
5 mol B ( 1 mol A / 2 mol B) = 2.5 mol A needed to be consumed completely

Therefore, the limiting would be reactant A and the excess would be reactant B. The amount of the excess would be:

5 mol B - 4 mol B = 1 mol B <LAST OPTION

Electrical charges of ionic bonds

Answer : option a) 84explanation :

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.