Question

An aqueous solution of calcium hydroxide is standardized by titration with a 0.117 M solution of hydrobromic acid.

Required:
a. If 24.7 mL of base are required to neutralize 16.0 mL of the acid. What is the molarity of the calcium hydroxide solution?
b. What volume of a 0.270 M hydrochloric acid solution is required to neutralize 22.8 mL of a 0.113 M calcium hydroxide solution?
c. How many milliliters of 10.8 M hydrobromic acid solution should be used to prepare 2.50 L of 0.400 M ?

Answer 1

a) 0.0379 M

b) 24.89 mL

c) 0.09 mL

Step-by-step explanation:

The equation of the reaction is:

2HBr(aq) + Ca(OH)2(aq) ---> CaBr2(aq) + 2H20(l)

a)

Concentration of acid CA = 0.117 M

Concentration of base CB= ??

Volume of acid VA = 16.0 ml

Volume of base VB = 24.7 ml

number of moles of acid NA = 2

number of moles of base NB= 1

From;

CA VA/CB VB = NA/NB

CAVANB =CBVBNA

CB = CAVANB/VBNA

CB = 0.117 *16 * 1/ 24.7 *2

CB = 1.872/49.4

CB = 0.0379 M

b)

CA = 0.270 M

CB = 0.113 M

VA = ??

VB =22.8mL

NA =2

NB =1

From;

CA VA/CB VB = NA/NB

CAVANB =CBVBNA

VA = CBVBNA/CANB

VA = 0.113 * 22.8 * 2/0.207 *1

VA = 24.89 mL

c)

using the dilution formula

C1V1 =C2V2

Where:

C1= initial concentration =10.8 M

V1 = initial volume = ??

C2= final concentration =0.400 M

V2= final volume = 2.5 L

V1 = C2V2/C1

V1 = 0.400 * 2.5/10.8

V1 = 0.09 mL