Chemistry Study Material

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1. An indicator defines any substances that changes in color in response to chemical change. An
indicator solution drop is added to titration at the start to allow determination of the end point of
a reaction since at the reaction end point the indicator will change the color to a different color.
There is a change in color at the endpoint of a reaction since any unreacted molecules in excess
of the needed ones to attain the endpoint would undergo a reaction with the molecules of the
indicator. This results in a change in the structure of the molecules of the indicator thereby
having a change in the color.
2. The unknown solution goes to the burette. The solution will then be titrated against the titrant
that would aid in calculations that will be used in its identification.
3. Mole if acid: base in the reaction=2:3
Ca (OH) 2 is the base while H3PO4 is the acid
4. Strong base-weak acid. A reaction between a strong base and a weak acid results in excess
OH- ions in the solution that render the pH of the solution to be alkaline hence more than 7
5. Equation for reaction
HCl+ NaOH NaCl + H2O
Moles of HCl used=0.015*18.7/1000=0.0002805 moles
Mole ratio of HCl: NaOH=1:1
Moles of NaOH used=0.0002805 moles
Molarity of NaOH=0.0002805/15*1000
=0.0187 M