The decomposition of phosphine (PH₃) on tungsten at low pressure is a first-order reaction. It is because the:

1. rate is proportional to the surface coverage

2. rate is inversely proportional to the surface coverage

3. rate is independent of the surface coverage

4. rate of decomposition is very slow

The characteristics associated with adsorption are:

1. ∆G, ∆H, and ∆S are all negative.
2. ∆G and ∆H are negative, but ∆S is positive.
3. ∆G and ∆S are negative, but ∆H is positive.
4. ∆G is negative, but ∆H and ∆S are positive.