Sulfur smells like rotten egg and is yellow...
Answer:
There are 10.0 moles of beryllium oxide in a 250 grams sample of the compound.
Explanation:
We can calculate the number of moles (η) of BeO as follows:

Where:
m: is the mass = 250 g
M: is the molar mass = 25.0116 g/mol
Hence, the number of moles is:

Therefore, there are 10.0 moles of beryllium oxide in a 250 grams sample of the compound.
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2Mg+ O₂= 2MgO
The charge of Mg is+2 and the charge of Oxygen is -2. 2 oxygen atoms will have a charge of -4 so the Mg atoms have to equal +4. A coefficient of 2 for the Mg atoms will balance it out
Answer: This is because the number of shell increases .
Explanation: On moving from left to write on the periodic table the reactivity of non metals increases because number of shells increases and the force with which the nucleus hold electrons decreases.
Answer:
V= 0.147 L
Explanation:
This is simply the application of combined gas law twice, to find the unknowns.
Combined gas law states that: 
P= pressure of air
V= volume of air
n= moles of air
R= Universal gas constant ( 0.08205 L atm mol⁻¹ K⁻¹)
T= Absolute temperature in kelvin.

Now, applying the same gas law at 483K and substituting for n

V= 
V= 0.147 L