Final answer:
The amount of rubidium needed to equal the pressure wave of a standard hand grenade cannot be determined.
Step-by-step explanation:
To determine how much rubidium would be needed to equal the pressure wave of a standard hand grenade, we need to compare the pressure generated by the two. However, without specific information about the pressure wave of a hand grenade and its comparison to rubidium, it is not possible to calculate the exact amount of rubidium needed. Therefore, the correct answer is that we cannot determine the amount of rubidium required.