1-12 Describe how isotopes can be separated

1-12-1. Consider a gas containing 0.7% ²³₅UF₆ and 99.3% ²³₈UF₆. If the gas is contained in chamber A, as illustrated below, and is allowed to escape through a pinhole into vacuum chamber B, the percentage of ²³₅UF₆ in the gas that initially emerges in chamber B will be...
A. higher than 0.7%,
B. lower than 0.7%,
C. still 0.7%

1-12-2. A sample of H₂ molecules, containing protium (¹H) and deuterium (²H) isotopes, is injected into a mass spectrometer. How many signals due to H₂⁺ ions can we expect to observe?
A. 0, B. 1, C. 2, D. 3