Answer:
A general instrument, which is used to determine the concentration of hydrogen ion within the aqueous solution is known as a pH meter. The meter helps in determining the alkalinity or acidity, which is articulated in the form of pH. It is also called a potentiometric pH meter as it helps in finding the variation in electrical potential between a reference electrode and a pH electrode. This electrical potential variation is associated with the pH of the solution.
The potentiometric pH meter comprises a pair of electrodes and a basic electronic amplifier, some may even comprise a combination electrode and some sort of display that demonstrates pH units. The potentiometric pH meter generally exhibits a reference electrode or a combination electrode, and a glass electrode. The probes or electrodes are administered within a solution whose pH values are needed to be determined.
Answer: The correct option is (c). The total pressure doubles.
Solution:
Initially, only 4 moles of oxygen gas were present in the flask.
(
) ( according to Dalton's law of partial pressure)
....(1)
= Total pressure when only oxygen gas was present.
Final total pressure when 4 moles of helium gas were added:
![X'_{O_2}=\frac{4}{8}=\farc{1}{2},X_{He}=\frac{4}{8}=\frac{1}{2}](https://tex.z-dn.net/?f=X%27_%7BO_2%7D%3D%5Cfrac%7B4%7D%7B8%7D%3D%5Cfarc%7B1%7D%7B2%7D%2CX_%7BHe%7D%3D%5Cfrac%7B4%7D%7B8%7D%3D%5Cfrac%7B1%7D%7B2%7D)
partial pressure of oxygen in the mixture :
Since, the number of moles of oxygen remains the same, the partial pressure of oxygen will also remain the same in the mixture.
![p_{O_2}=Tp_2\times X'_{O_2}=Tp_2\times \frac{1}{2}](https://tex.z-dn.net/?f=p_%7BO_2%7D%3DTp_2%5Ctimes%20X%27_%7BO_2%7D%3DTp_2%5Ctimes%20%5Cfrac%7B1%7D%7B2%7D)
= Total pressure of the mixture.
from (1)
![Tp_1=Tp_2\times X'_{O_2}=Tp_2\times \frac{1}{2}](https://tex.z-dn.net/?f=Tp_1%3DTp_2%5Ctimes%20X%27_%7BO_2%7D%3DTp_2%5Ctimes%20%5Cfrac%7B1%7D%7B2%7D)
On rearranging, we get:
![Tp_2=2\times Tp_1](https://tex.z-dn.net/?f=Tp_2%3D2%5Ctimes%20Tp_1)
The new total pressure will be twice of initial total pressure.
To figure out the ratios of these compounds, it is important to remember that the charge of these compounds must be <em>
neutral</em>.
So in order to make them neutral, you must have specific ratios:
![Na^{+}: Br^{-} =1:1](https://tex.z-dn.net/?f=Na%5E%7B%2B%7D%3A%20Br%5E%7B-%7D%20%20%3D1%3A1)
; This is true because they both have a charge of magnitude of 1.
![Al^{3+}: Cl^{-}=1:3](https://tex.z-dn.net/?f=%20Al%5E%7B3%2B%7D%3A%20Cl%5E%7B-%7D%3D1%3A3%20%20)
; We need 3 chlorine atoms because we need to balance out the charge from the 3+ charge of aluminum - therefore since chlorine has a 1- charge, we need 3 atoms.
![Mg^{2+}: O^{2-}=1:1](https://tex.z-dn.net/?f=Mg%5E%7B2%2B%7D%3A%20O%5E%7B2-%7D%3D1%3A1)
; The charges of the magnesium (2+) are balanced with the oxygen charge (2-).
![Al^{3+}: O^{2-}=2:3](https://tex.z-dn.net/?f=%20Al%5E%7B3%2B%7D%3A%20O%5E%7B2-%7D%3D2%3A3%20%20)
; This is correct because if charges are like this, you must find the least common factor in order to know the ratio. The LCF is 6, therefore, for the atom with a 3+ charge, you need 2 of them, and for the atom with a 2- charge, you need 3 of them. This keeps the charge neutral.