Answer : The chemical formula for the compound is, 
Explanation :
When the element 'M' react with the
to give
.
The balanced chemical reaction is,

In this reaction, 'M' is in mono-atomic form and
is in diatomic form.
By the stoichiometry,
2 moles 'M' react with the 1 mole of
to give 2 moles of
.
Therefore, the chemical formula of the compound is, 
I think the correct answer is option 3. CaCl2 is the compound that is an electrolyte when dissolved in water. An electrolyte is a substance that conducts electricity in solution. Calcium Chloride when in solution dissociates into ions which allows the flow of current in the solution.
Answer: 996 mmHg
Explanation:
According to avogadro's law, 1 mole of every substance occupies 22.4 L at NTP, weighs equal to the molecular mass and contains avogadro's number
of particles.
According to the ideal gas equation:

P = Pressure of the gas = ?
V= Volume of the gas = 25.5 L
T= Temperature of the gas = 13°C = (273+13) K = 286K
R= Gas constant = 0.0821 atmL/K mol
n= moles of gas= 1.42
(760mmHg=1atm)
Thus pressure of this gas sample is 996 mm Hg.
Answer:
N=2
H=6
Explanation:
1.Balance a chemical equation in terms of moles.
2.Use the balanced equation to construct conversion factors in terms of moles.
3.Calculate moles of one substance from moles of another substance using a balanced chemical equation.
The law of conservation of matter says that matter cannot be created or destroyed. In chemical equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each element in the products.
(P.s it could also be where you have to solve it in which you have to simplify it first then solve it.) like adding them all up.
Hope this is the answer. :)
I think the correct answer from the choices listed above is the last option. The pressure of an enclosed gas depends on the number of molecules in a unit volume and their average kinetic energy, its chemical composition, the altitude about sea level and the number of atoms per molecule. Hope this helps. Have a nice day.