Question

1 mol of hydrogen gas and 1 mol of iodine vapour were mixed and allowed to react. After t seconds 0.8 mol of hydrogen remained.

The number of miles of hydrogen iodide formed at t seconds was..
A) 0.2
B) 0.4
C) 0.8
D) 1.6

The answer is B but please explain how you work this out?

Answer 1

At the beginning there was just 1 mole of hydrogen and 1 mole of iodin.
The reaction goes:

`H_2+I_2\Rightarrow\ 2HI`
One mole of hydrogen goes with one mole of iodin, creating 2 moles of product.
If 0.8 of hydrogen remaind, it means that 1-0.8=0.2 reacted.
So:
1 mole H2 react with 1 mole I2 creating 2 moles of products.
So 0.2 of hydrogen reacted with 0.2 mole of iodin creating 0.4 moles.

`1\ mole\ H_2\ ---\ 2\ moles\ HI\\ 0.2\ mole\ \ \ ---\ x\\ x=0.4`