Answer: e) 9.43
Explanation: A buffer solution is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid and the pH of the buffer is calculated using Handerson equation:
There are 25 mL of 0.50 M 
which is a weak base. 25 mL of 0.20 M HCl, a strong acid are added. Ammonia reacts with HCl to form its conjugate acid, ammonium ion. The net ionic equation will be:
From above reaction, ammonia and HCl react in 1:1 mol ratio. Let's calculate the moles of each we have before the reaction. There is also, 1:1 mol ratio between HCl and ammonium ion.
moles of ammonia = 
= 0.0125 mol
moles of HCl = 
= 0.005 mol
Excess moles of ammonia = 0.0125 - 0.005 = 0.0075 mol
moles of ammonium ion formed = 0.005 mol
Total volume of the solution = 0.025 mL + 0.025 mL = 0.050 L
concentration of ammonia in buffer = 
= 0.15 M
concentration of ammonium ion in buffer = 
= 0.10 M
pKa is calculated from given Ka as:
pKa = 9.25
Plug in the values in Handerson equation:
pH = 9.25 + 0.18
pH = 9.43
So, the correct choice is e) 9.43 .
Answer: c. 
Explanation:
Solubility product is defined as the equilibrium constant in which a solid ionic compound is dissolved to produce its ions in solution. It is represented as 
The equation for the ionization of the calcium carbonate is given as:
We are given:
By stoichiometry of the reaction:
1 mole of 
gives 1 mole of 
and 1 mole of 
.
Expression for the equilibrium constant of will be:
![K_{sp}=[Ca^{2+}][CO_3^{2-}]](https://tex.z-dn.net/?f=K_%7Bsp%7D%3D%5BCa%5E%7B2%2B%7D%5D%5BCO_3%5E%7B2-%7D%5D)
![3.8\times 10^{-9}=[s][s]](https://tex.z-dn.net/?f=3.8%5Ctimes%2010%5E%7B-9%7D%3D%5Bs%5D%5Bs%5D)
Hence, the concentration in moles/liter of calcium ion in a saturated solution of calcium carbonate is
Explanation:
both reduction and oxidation are occurring simultaneously, this is known as a redox reaction. An oxidizing agent is substance which oxidizes something else. In the above example, the iron(III) oxide is the oxidizing agent. A reducing agent reduces something else
46.16% of sugar is oxygen
