Question

11C. Potassium hydrogen phthalate is a solid, monoprotic acid frequently used in the laboratory to standardize strong base solutions. It has the unwieldy formula of KHC8H4O4. This is often written in shorthand notation as KHP .If 3.41 grams of KHC are needed to exactly neutralize 31.2 mL of a potassium hydroxide solution, what is the concentration of the base solution?
13B.
H3AsO4 + H2C2O4—--------2CO2 + H3AsO3+ H2O

In the above redox reaction, use oxidation numbers to identify the element oxidized, the element reduced, the oxidizing agent and the reducing agent.



name of the element oxidized:


name of the element reduced:


formula of the oxidizing agent:


formula of the reducing agent:

Answer 1

For the reactants,

• The oxidation number of hydrogen = +1
• The oxidation number of oxygen = -2
• The oxidation number of arsenic = +5
• The oxidation number of carbon = +3

For the products,

• The oxidation number of hydrogen = +1
• The oxidation number of oxygen = -2
• The oxidation number of arsenic = +3
• The oxidation number of carbon = +4

Here, arsenic (+5 to +3) and carbon (+3 to +4) are the only oxidation numbers changing.

Note that an increase in oxidation number means electrons are lost. Thus oxidation is occurring, and a decrease in oxidation number means electrons are being gained, and thus reduction is occurring.

Also, the compound that contains the element being oxidized is the reducing agent, and the compound that contains the element being reduced is the oxidizing agent.

So, the answers are:

name of the element oxidized: Carbon

name of the element reduced: Arsenic

formula of the oxidizing agent: $\text{H}_{3}\text{AsO}_{4}$

formula of the reducing agent: $\text{H}_{2}\text{C}_{2}\text{O}_{4}$