Answer:
Physical changes occur when objects or substances undergo a change that does not change their chemical composition. This contrasts with the concept of chemical change in which the composition of a substance changes or one or more substances combine or break up to form new substances.
Explanation:
It takes 333.3 s for Oxygen to diffuses
<h3>Further explanation </h3>
Graham's law: the rate of effusion of a gas is inversely proportional to the square root of its molar masses or
the effusion rates of two gases = the square root of the inverse of their molar masses:
or
r₁ H₂ = 300 cm³/50 s=6 cm³/s
M₁ H₂ = 2 g/mol
M₂ O₂ = 32 g/mol
the diffusion time of Oxygen :
CuCO₃ ---T--> CuO↓ + CO₂ ↑
CO₂ escapes to the atmosphere (it's a gas)