<u>Answer:</u> The volume of concentrated hydrochloric acid required is 16.53 mL
<u>Explanation:</u>
To calculate the volume of concentrated solution, we use the equation:

where,
are the molarity and volume of the concentrated solution
are the molarity and volume of diluted solution
We are given:
Conversion factor: 1 L = 1000 mL

Putting values in above equation, we get:

Hence, the volume of concentrated hydrochloric acid required is 16.53 mL
It is B, and also for a moment I didn't understand that 4.69 x 10^22. I almost did this whole problem wrong.
Answer:
C is the excess reactant.
Explanation:
Reaction is C + O2 --> CO2
1mol of C required to react with 1mol O2
Therefore 15 - 10 = 5moles of C will be in excess
The answer would be D Heterogeneous