**Answer:**

Sorry my task time about to run out : (

**Explanation:**

To determine the molar mass of the unknown gas, we use Graham's Law of Effusion where it relates the effusion rates of two gases with their molar masses. It is expressed as r1/r2 = √M2/M1. We calculate as follows:

Let 1 = argon gas 2 = unknown gas

r2 = 0.91r1r1/r2 = 1/0.91

1/0.91 = √M2/M1 = √M2/40M2 = 48.30 g/mol

Different between potential energy and mechanical energy

Alpha particles; they can be blocked with a sheet of paper