<u>Answer:</u> The mass of iron in the ore is 10.9 g
<u>Explanation:</u>
We are given:
Mass of iron (III) oxide = 15.6 g
We know that:
Molar mass of Iron (III) oxide = 159.69 g/mol
Molar mass of iron atom = 55.85 g/mol
As, all the iron in the ore is converted to iron (III) oxide. So, the mass of iron in iron (III) oxide will be equal to the mass of iron present in the ore.
To calculate the mass of iron in given mass of iron (III) oxide, we apply unitary method:
In 159.69 g of iron (III) oxide, mass of iron present is 
So, in 15.6 g of iron (III) oxide, mass of iron present will be = 
Hence, the mass of iron in the ore is 10.9 g
hi
Thus, a sodium hydroxide solution has a greater OH– concentration than the same concentration solution of NH3. At the same concentrations, the pH of the NaOH solution is greater (more basic) than the NH3 solution.
Answer: Option (B) is the correct answer.
Explanation:
An aqueous solution that consists of a mixture of weak base and its conjugate acid or a weak acid and its conjugate base is known as a buffer.
When we add a strong acid or base into this mixture then the change in pH of this mixture is very small.
In a buffer solution, pH depends on the ratio of concentration of base divided by concentration of acid.
It is known that for a given temperature, the value of 
remains constant.
Therefore, relation between pH and will be as follows.
pH = 
Thus, we can conclude that the purpose of an acid-base buffer is to maintain a relatively constant pH in a solution.
