Answer:
The molar mass of the unknown gas is 
Explanation:
Let assume that the gas is O2 gas
O2 gas is to effuse through a porous barrier in time t₁ = 4.98 minutes.
Under the same conditions;
the same number of moles of an unknown gas requires time t₂ = 6.34 minutes to effuse through the same barrier.
From Graham's Law of Diffusion;
Graham's Law of Diffusion states that, at a constant temperature and pressure; the rate of diffusion of a gas is inversely proportional to the square root of its density.
i.e

where K = constant
If we compare the rate o diffusion of two gases;

Since the density of a gas d is proportional to its relative molecular mass M. Then;

Rate is the reciprocal of time ; i.e

Thus; replacing the value of R into the above previous equation;we have:

We can equally say:






Hydrocarbons. They usually burn. In fact, I can't think of one that does not.
Answer:
Yes
Explanation:
Electrolysis is an example of redox reaction because reduction takes place at cathode and oxidation takes place at anode and both of these reactions take place simultaneously.
Balanced equation:
Ca(OH)2+H2SO4=CaSO4+2 H20<span />
It important to test the crucible for cracks before heating it because it can break while performing the chemical reaction.
The crucible and the lid should be inspected to check for the before heating it to prevent the breaking while performing the reactions. if there are some breaks in the crucible then if we heat the crucible it can lead to breaking of the whole crucible and the material from the crucible to come out and it will come in contact with the lid.
The crucible plays a important role while preforming the reactions, so. it important to check the cracks of the crucible before the heating of the crucible.
To learn more about crucible here
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