2 nitrogen atoms, 4 hydrogen atoms and 3 oxygen atoms
There are 1000 meters in 1 Kilometer.
Hope this helps you. :)
I can tell you're not very educated because everyone knows that breathing pure oxygen for long periods of time can sometimes hurt us. Oxygen in lower levels, such as levels found in atmosphere are just right for us to breathe. Get a life and stop trying to scare young kids that just want help on their homework.
Explanation :
As we know that the Gibbs free energy is not only function of temperature and pressure but also amount of each substance in the system.
where,
is the amount of component 1 and 2 in the system.
Partial molar Gibbs free energy : The partial derivative of Gibbs free energy with respect to amount of component (i) of a mixture when other variable 
are kept constant are known as partial molar Gibbs free energy of 
component.
For a substance in a mixture, the chemical potential 
is defined as the partial molar Gibbs free energy.
The expression will be:
where,
T = temperature
P = pressure
is the amount of component 'i' and 'j' in the system.
Answer:
Explanation:
The usefulness of a buffer is its ability to resist changes in pH when small quantities of base or acid are added to it. This ability is the consequence of having both the conjugate base and the weak acid present in solution which will consume the added base or acid.
This capacity is lost if the ratio of the concentration of conjugate base to the concentration of weak acid differ by an order of magnitude. Since buffers having ratios differing by more will have their pH driven by either the weak acid or its conjugate base .
From the Henderson-Hasselbach equation we have that
pH = pKa + log [A⁻]/[HA]
thus
0.1 ≤ [A⁻]/[HA] ≤ 10
Therefore the log of this range is -1 to 1, and the pH will have a useful range of within +/- 1 the pKa of the buffer.
Now we are equipped to answer our question:
pH range = 3.9 +/- 1 = 2.9 through 4.9
