**Question 3**Choose the best indicator to use in the titration of a weak base (CH₃NH₂) methylamine with HCl.**a.** - **Indicator:** Methyl Orange - **Titration Range:** 3.1 – 4.4 - **Color Change:** Red to orange **b.** - **Indicator:** Methyl Red - **Titration Range:** 4.2 – 6.3 - **Color Change:** Red to yellow **c.** - **Indicator:** Bromothymol Blue - **Titration Range:** 6.2 – 7.6 - **Color Change:** Yellow to blue **d.** - **Indicator:** Thymol Blue - **Titration Range:** 8.0 – 9.6 - **Color Change:** Yellow to blue **e.** - **Indicator:** Alizarin Yellow - **Titration Range:** 10.0 – 12.0 - **Color Change:** Colorless to yellow *Note: Moving to the next question prevents changes to this answer.*

The acid- base reaction of methylamine and HCl is given as:HCl + CH3NH2 ⇌ CH3NH3+ + Cl- At the equivalence point, the number of mole of the acid added is equal to the number of mole of base present. Considering that the concentrations of base and acid are equal (1M), the concentration of the conjugate acid, CH3NH3+ can be determined as follows: Since equal volumes of the acid and base should be mixed, and since they are additive, the concentration of CH3NH3+ will be half the initial concentration of CH3NH2 . Thus, [ CH3NH3+ ] =0.5 M The conjugate acid that will be the major species at the equivalence point, will be the only significant source of H+ in the solution. CH3NH3+ ⇌ CH3NH2 + H+Ka = CH3NH2 H+CH3NH3+ = x20.5-xKb (CH3NH2) = 5.0×10-4Ka = KwKb = 10-145.0×10-4 = 0.2×10-10x20.5-x = 0.2×10-10x = H+ = 0.32×10-5 pH = -log H+pH = -log 0.32×10-5 = 5.49pH at the equivalence point will be 5.49The indicator chosen should have titration range having pH 5.49Out of the given indicators, Methyl red is the indicator having titration range of 4.2 to 6.3 and color change red to yellow.So, the correct option is:B. Indicator: Methyl red Titration range: 4.2-6.3 Color change: Red to yellow

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Chemistry

Choose the best indicator to use in the titration of a weak base (CH3NH2) methylamine with HCl. Indicator Titration Range Color Change Methyl Orange 3.1- 4.4 red to orange a. Indicator Titration Range Color Change Ob. Methyl red 4.2-6.3 red to yellow Indicator Titration Range Color Change Oc. Bromothymol blue 6.2 - 7.6 yellow to blue Indicator Titration Range Color Change Od. Thymol blue 8.0 - 9.6 yellow to blue Indicator Titration Range Color Change Alizarin yellow 10.0 - 12.0 Colorless to yellow e.

Choose the best indicator to use in the titration of a weak base (CH3NH2) methylamine with HCl. Indicator Titration Range Color Change Methyl Orange 3.1- 4.4 red to orange a. Indicator Titration Range Color Change Ob. Methyl red 4.2-6.3 red to yellow Indicator Titration Range Color Change Oc. Bromothymol blue 6.2 - 7.6 yellow to blue Indicator Titration Range Color Change Od. Thymol blue 8.0 - 9.6 yellow to blue Indicator Titration Range Color Change Alizarin yellow 10.0 - 12.0 Colorless to yellow e.

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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