Answer : The correct expression will be:

Explanation :
The chemical reactions are :
(1)

(2)

The final chemical reaction is :

Now we have to calculate the value of
for the final reaction.
Now equation 1 is multiply by 2 and then add both the reaction we get the value of 'K'.
If the equation is multiplied by a factor of '2', the equilibrium constant will be the square of the equilibrium constant of initial reaction.
If the two equations are added then equilibrium constant will be multiplied.
Thus, the value of 'K' will be:

Where does most of the mass of the universe come from? In ordinary matter, most of the mass is contained in atoms, and the majority of the mass of an atom resides in the nucleus, made of protons and neutrons. Protons and neutrons are each made of three quarks.
<span>You can answer this question by getting the atomic number and atomic mass of Oxygen from a periodic table. There you will find that the atomic number is 8, that means, by definition, that it has 8 protons. This is, because atomic number is defined as the number of protons of an element. Given that the atom is neutral, that implies that the atoms have the same number of electrons than protons. So you already know that the oxygen atoms has 8 protons and 8 electrons. The number of neutrons can vary, which is what defines the isotopes. Given that the atomic mass of oxygen is 15.999, that means that most atoms of oxygen has 8 neutrons (8 protons +8 neutrons = 16 atomic mass). But you can not be sure that a specific atom of oxygen has 8 neutrons, nevertheless, given that the other options are discarded (because they do not have 8 protons and 8 electrons), the only correct answer is the option A. 8 protons, 8 electrons, and 8 neutrons.</span>
Answer:
The volume of CO2 produced is 6.0 L (option D)
Explanation:
Step 1: Data given
Volume of oxygen = 3.0 L
Carbon monoxide = CO = in excess
Step 2: The balanced equation
2 CO (g) + O2 (g) → 2 CO2 (g)
Step 3: Calculate moles of O2
1 mol of gas at STP = 22.4 L
3.0 L = 0.134 moles
Step 3: Calculate moles of CO2
For 2 moles CO we need 1 mol of O2 to produce 2 moles of CO2
For 0.134 moles O2 we'll have 2*0.134 = 0.268 moles CO2
Step 4: Calculate volume of CO2
1 mol = 22.4 L
0.268 mol = 22.4 * 0.268 = 6.0 L
The volume of CO2 produced is 6.0 L