Answer:
1116 g.
Explanation:
The balanced equation for the reaction is given below:
4Na + O₂ —> 2Na₂O
From the balanced equation above,
1 mole of O₂ reacted to produce 2 moles of Na₂O.
Next, we shall determine the theoretical yield of Na₂O. This can be obtained as follow:
From the balanced equation above,
1 mole of O₂ reacted to produce 2 moles of Na₂O.
Therefore, 9 moles of O₂ will react to produce = 9 × 2 = 18 moles of Na₂O.
Finally, we shall determine the mass in 18 moles of Na₂O. This can be obtained as follow:
Mole of Na₂O = 18 moles
Molar mass of Na₂O = (23×2) + 16
= 46 + 16
= 62 g/mol
Mass of Na₂O =?
Mass = mole × molar mass
Mass of Na₂O = 18 × 62
Mass of Na₂O = 1116 g
Thus, the theoretical yield of Na₂O is 1116 g.
To be honest I don’t even know
1st find the pOH = 14 - 4.75 = 9.25
then do 10^-9.25 = 5.62x10^-10 OH- concentration
Answer : The molar heat of solution of KCl is, 17.19 kJ/mol
Explanation :
First we have to calculate the heat of solution.

where,
q = heat produced = ?
c = specific heat capacity of water = 
= change in temperature = 0.360 K
Now put all the given values in the above formula, we get:


Now we have to calculate the molar heat solution of KCl.

where,
= enthalpy change = ?
q = heat released = 460.8 J
m = mass of
= 2.00 g
Molar mass of
= 74.55 g/mol

Now put all the given values in the above formula, we get:


Therefore, the molar heat of solution of KCl is, 17.19 kJ/mol
Answer: 72 grams of
are needed to completely burn 19.7 g 
Explanation:
According to avogadro's law, 1 mole of every substance weighs equal to molecular mass and contains avogadro's number
of particles.
To calculate the number of moles, we use the equation:

Putting in the values we get:


According to stoichiometry:
1 mole of
requires 5 moles of oxygen
0.45 moles of
require=
moles of oxygen
Mass of 
72 grams of
are needed to completely burn 19.7 g 