Question

There are 8.340 x 10²⁵ I₂ molecules and 4.76 x 10³⁰ F₂ molecules in a container. These are made to react and form IF₇ molecules. Which is the limiting reactant (LR) and which is the excess reactant (ER)? Use factor label method for your calculations.

Select one:

a. LR: I; ER: F

b. LR: F; ER: I

c. LR: F₂; ER: I₂

d. LR: I₂; ER: F₂

Answer 1

Reaction is

I₂ + 7 F₂ ...............> 2 IF₇

In this reaction, 1 mole I₂ react with 7 mole F₂ to form 2 mole IF₇.

we have

8.340 x 10²⁵ I₂ molecules and 4.76 x 10³⁰ F₂ molecules

mole of I2 molecules = 8.340 x 10²⁵ / 6.023 * 10^23 = 138.47 mole.

and

mole of F2 = 4.76 x 10³⁰ / 6.023 * 10^23 = 7.903 * 10^6 mole.

138.47 mole I2 should react with 138.47 * 7 = 969.29 mole F2 but there are 7.903 * 10^6 mole F2.

so

I2 is the limiting reactant (LR)

and

F2 remain in excess (ER).

option d. LR: I₂; ER: F₂ is the answer.