Post-Lab 3: Practice Titration, Potassium Hydrogen Phthalate (KHP) PDF

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Post lab 3 for CHM 3120C...

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Post-Lab 3: Practice Titration, Potassium Hydrogen Phthalate (KHP) Christian Claros 3/04/21 CHM 3120C – 002 Group A

Quantitative Observation Moles of KHP =

𝑀𝑎𝑠𝑠 𝐾𝐻𝑃 (𝑔)

𝑀𝑜𝑙𝑎𝑟 𝑀𝑎𝑠𝑠 𝑜𝑓 𝐾𝐻𝑃 (

𝑔 ) 𝑚𝑜𝑙𝑒

# 𝑜𝑓 𝑚𝑜𝑙𝑒 𝑠𝑜𝑙𝑢𝑡𝑒

Molarity = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝑙) Percent Error:

𝐴𝑐𝑡𝑢𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 − 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒

× 100 % = % 𝐸𝑟𝑟𝑜𝑟

Average: 𝑋 = (𝑋1 + 𝑋2 )/𝑁 𝑛

Standard deviation (s): = ∑

(𝑋𝑖 𝑋) 2

𝑖=1 𝑁−1

Table 1: Titration (Standardization of NaOH solution) Trail 1 Trial 2 Mass of a weighing

Trial 3

0.2321 g

0.2364 g

0.2367 g

0.9312 g

0.9377 g

0.9318 g

0.9312 g − 0.2321

0.9377 g − 0.2364

0.9318 g − 0.2367

g = 0.6991 g

g = 0.7013 g

g = 0.6951 g

paper Mass of a weighing paper and dried KHP Mass of dried KHP

# of moles, KHP

0.6991 g

204.22(

𝑔

)

𝑚𝑜𝑙𝑒

0.7013 g

=

204.22(

𝑔

)

𝑚𝑜𝑙𝑒

=

0.6951 g

204.22(

𝑔

)

𝑚𝑜𝑙𝑒

=

3.423 × 10-3 mol.

3.434 × 10-3 mol.

3.404 × 10-3 mol.

0.5 mL

0.1 mL

1.1 mL

33.75 mL

33.6 mL

34.4 mL

Volume of NaOH

33.75 mL − 0.5

33.6 mL − 0.1

34.4 mL – 1.1 mL

used

mL = 33.25 mL

mL = 33.5 mL

= 33.3 mL

Volume of NaOH (Initial) Volume of NaOH (Final)

Molarity of the NaOH solution % Error

0.003423 mol. 0.03325 𝐿

=

0.003434 mol. 0.0335 𝐿

0.1029 M 0.1029 M −0.1 M 0.1 𝑀

0.1025 M ×

100% = 2.9 %

0.1025 M −0.1 M 0.1 𝑀

0.003404 mol.

=

0.0333 𝐿

0.1022 M ×

100% = 2.5 %

Average Molarity of the NaOH solution and STD: Standard Deviation: √(

=

0.1022 M −0.1 M 0.1 𝑀

×

100% = 2.2 %

0.1029 𝑀 + 0.1025 𝑀 + 0. 1022 𝑀 3

= 0.1025 M

(0.1029 M − 0.1025 M )^2+(0.1025 M − 0.1025 M )^2+(0.1022 M − 0.1025 M )^2 3−1

)= ±

3.536 × 10-4 M Average ± Standard Deviation: 0.1025 M ± 3.536 × 10-4 M Research Questions 1. What is the correct way to handle a burette and an Erlenmeyer flask during a titration? The correct way of handling a burette and an Erlenmeyer flask during a titration is to have your right hand on the stopcock, left hand swirling the flask with your eyes on the solution to be able to see the indicator.

2. Provide at least 2 different examples of desiccant material and at least 2 different styles of desiccator and explain how they function differently. Two types of desiccant materials are molecular sieves and synthetic polymers. Two styles of desiccator are montmorillonite clay and silica gel. The clay is a natural absorbent made by dried magnesium aluminum silicate. The clay works great under 120 °F because it pulls moisture well below that temperature. Silica gel works well up to 220 °F for absorbing moisture in the air. (1) 3. Why is water boiled prior to the preparation of NaOH standard solution? Explain briefly. Water is boiled to remove unwanted carbon dioxide from the water, carbon dioxide and sodium hydroxide react and form carbonate ion when together. (2) 4. (¶) What is standardization in acid-base chemistry? What constitutes a standard in analytical chemistry? Give types and examples. A standardization is when you determine the concentration of a solution. A standard is a reference made of known concentrations of substances used for quantitative analysis. Types of standardization are acid-base titrations that uses exact volumes of one substance to react with a known amount of the other and using the pH as the indicating point. There is also redox titrations that determines the concentration of an analyte that contains reducing or oxidizing agents. (3) 5. (¶) In the following graph depicting a titration curve for weak acid vs strong base (titrant), explain the chemistry occurring (in regards to chemicals and their states, equilibria) at four points a, b, c, and d indicated.

At point a we have the highest [H+] during the titration. At point b is where there is a low amount of [H+] so any drop of [OH-] will affect the pH of the solution immensely. At c is the equivalence point where the moles of H+ equals the moles of OH-. At d we have majority of OH- in the solution, so small additions of H+ will not affect the pH much.

References (1)

Desiccant Types http://sorbentsystems.com/desiccants_types.html (accessed Mar 2, 2021).

(2)

Kim, J. The Standardization of NaOH and KHP https://www.odinity.com/standardization-naoh-khp/ (accessed Mar 2, 2021).

(3)

Types of Titration (Titration Chemistry) https://byjus.com/chemistry/types-oftitration/ (accessed Mar 2, 2021)....