Answer:C, atoms must balance positive and negative particles.
Explanation: Got it correct on edgenuity.
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Answer : The correct option is, (B) 
Solution :
According to the Graham's law, the rate of effusion of gas is inversely proportional to the square root of the molar mass of gas.

or,
..........(1)
where,
= rate of effusion of unknown gas = 
= rate of effusion of oxygen gas = 
= molar mass of unknown gas = ?
= molar mass of oxygen gas = 32 g/mole
Now put all the given values in the above formula 1, we get:


The unknown gas could be carbon dioxide
that has approximately 44 g/mole of molar mass.
Thus, the unknown gas could be carbon dioxide 
Answer:
2Mg(s) +O₂(g) → 2MgO(s)
Explanation:
Mg(s) +O₂(g) → MgO(s)
When a chemical equation is balanced, the number of atoms of each element is equal on both sides of the arrow. We usually balance O and H last.
In this case, the number of Mg atoms is equal on both sides. Thus, let's move on to balance the O atoms. On the left side, there are 2 O atoms, while there is only 1 O atom on the left side. Thus, write a '2' in front of MgO.
Mg(s) +O₂(g) → 2MgO(s)
Now, the number of Mg atoms is not equal. Write a '2' in front of Mg to balance it.
2Mg(s) +O₂(g) → 2MgO(s)
The equation is now balanced with 2 Mg atoms and 2 O atoms on each side.