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A. Match each type of titration to its pH at the equivalence point. Weak acid, strong base Strong acid, strong base…

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Question “A. Match each type of titration to its pH at the equivalence point. Weak acid, strong base Strong acid, strong base…”

A. Match each type of titration to its pH at the equivalence
point.
Weak acid, strong base
Strong acid, strong base
Weak base, strong acid

pH less than 7
pH equal to 7
pH greater than 7

B. A 56.0 mL volume of 0.25 M HBr is titrated with 0.50 M KOH.
Calculate the pH after addition of 28.0 mL of KOH.

C. Consider the titration of 50.0 mL of 0.20 M NH3 (Kb=1.8 x 10^-5)
with 0.20 M HNO3. Calculate the pH after addition of 50.0 mL of the
titrant.

D. A 30.0 mL volume of 0.50 M CH3COOH (Ka = 1.8 x 10^-5) was
titrated with 0.50 M NaOH. Calculate the pH after addition of 30.0
mL of NaOH.

Answer

Concepts and Reason

Based on their pH value, solutions can be classified as acids or bases.

Titration refers to a method where a concentrated solution of a known substance is used to determine the concentration of an unknown solution. The solution to a known concentration is known as a titrant, while the solution to an unknown concentrated is known as an analyte.

pH is a measurement of the hydrogen ion in a solution. It is the negative logarithm for the H + concentration to base 10. It is the acidic strength of a solution.

Fundamentals

Acid: acid substance can accept or donate a proton.

Basis:Base substance can either accept a proton, or give two electrons.

Based on their pH value, solutions can be classified as acids or bases. The pH value of a solution determines whether it is acidic or basic. pH values less than 7 are considered acidic. pH values greater than 7 are considered to be basic.

pH can be determined by measuring the concentration of

within the solution.

The

pH

value is negative logarithm (base

10

) of the Hydrogen ion concentration

[н]

.


pH log,


Molarity: Mole is the ratio between the solution’s volume and the number of moles.



Number of moles Molarity (M)Volume of solution(V)(Units: moles/:Liter) Number of moles Molarity (M)x Volume of solution (V) O




KH0OH 1x1014 Here [H0lis the hydronium ion concentration [OH Jis the hydroxide ion concentration


K

is the Equilibrium constant.

К,

refers to the equilibrium reaction’s base dissociation and ionization constant.

К,

is the expression for the equilibrium reaction.


ОН + B* ВОН Гон Тв] К [Вн]


K.

refers to the expression of an acid dissociation constant or ionization factor for equilibrium reactions.

K.

is the expression for an equilibrium reaction.


NH4 NH H NH,H NH, К.


(A)


Weak acid, strong base = pH greater than 7 Strong acid, strong base pH equal to7 Weak acid, strong base = pH less than 7



(B)


Given: Volume of HBr= 56.0mL 0.056L Concentration of HBr = 0.25M



Concentration of KOH = 0.50M Volume of KOH=28.0mL - 0.028L



The reaction between KOH and HCl is as follows КОН (а) + нсІ(аq)—></figure><p>n,o(aq) + kCI “></a><br /> </a></p><p> <a href=

Concentration of OH = Concentration of KOH Moles of OH Concentration of KOHxVolume of KOH =0.50M 0.028L 0.014mol Concentratio



Moles of H Concentration of HClxVolume of HCl - 0.25Mx0.056L 0.014mol Moles of OH ion is equal to moles of H* ion. Therefore,


(C)


Given: Volume of NH 50.0mL =0.050L Concentration of NH, = 0.20M 18x10 Ky of NH



Concentration of HNO, 0.20M Volume of HNO = 50.0mL =0.050L



The reaction is: NH, (aq) H (aq)NH, moles of NH, Concentration of NH,xVolume of NH, = 0.050L*0.2M -0.01mol



Concentration of H* x Volume of H moles of H 0.050L*0.2M 0.01mol moles of NH, and moles of H are equal. Hence, it is the equ



Total volume of solution = 0.05L 0.05L 0.1L



moles of NH Concentration of NH Total volume of solution 0.01mol 0.1L = 0.1M



К,К, - К. w к, к, К, 1x101 1.8х105 %3D 5.6х1010


NH H* NH 1(м) С (м) Е(м) 0.1 0 0 X X 0.1-х х X


NH, NH [NH,H NH, H* к, 5.6x1010 (x)(x) (0.1-х) +



Neglect x in the denominator and assume x is very small as K, is very smal 5.6x10 10 0.1 x2 5.6x10 X 7.48x10




[H] pH= -log (*) pH log 7.48x10 = 5.13



Ans Part A


Weak acid, strong base = pH greater than 7 Strong acid, strong base pH equal to7 Weak acid, strong base = pH less than 7


Conclusion

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