Simulations Neutralization

Universiti Pendidikan Sultan Idris

TKU 3023 ICT in Chemistry Assignment: Simulation “Acid, Base and Salts – Neutralization”

By: Siti Khadijah Binti Ibrahim

D20081032329

Syamimi Binti Othman

D20081032370

Group : B Lecturer’s Name Slot

: Cik Asmayati Binti Yahaya

: Thursday, 1.00 p.m – 4.00 p.m

CONTENTS TOPIC

PAGE

Scientific Concept

1

Engage

3

Empower

5

Enhance

10

NEUTRALIZATION Teacher’s guide / Chemistry form 4 / Simulation Scientific Concept Neutralization is a chemical reaction whereby an acid and a base react to form water and a salt. The word "neutralization" is used because the acid and base properties of H+ and OH- are destroyed or neutralized.

Acid + Base → Salt + Water In the reaction, H+ and OH- combine to form HOH or H2O or water molecules. In an aqueous solution, solvated hydrogen ions (hydronium ions, H3O+) react with hydroxide ions (OH-) formed from the alkali to make two molecules of water. A salt is also formed. In non-aqueous reactions, water is not always formed; however, there is always a donation of protons. The following are some examples of neutralization reactions to form salts. 1) HCl + NaOH → NaCl + H2O 2) H2SO4 + 2 NH4OH → (NH4)2SO4 + 2 H2O 3) 2 NaOH + H2CO3 → N2CO3 + 2 NaOH The application of neutralization: Chemical titration methods are used for analyzing acids or bases to determine the unknown concentration. Either a pH meter or a pH indicator which shows the point of neutralization by a distinct color change can be employed. Simple stoichiometric calculations with the known volume of the unknown and the known volume and molarity of the added chemical gives the molarity of the unknown. Applications in daily life: 1) Excess gastric acid in the stomach (acid indigestion) is typically neutralized by the ingestion of sodium bicarbonate (NaHCO3) or another neutralizing agent such as an antacid. 2) Neutralization can also be used to reduce the pain of insect and plant stings. Bee stings can be neutralized with alkalis and wasps with acids. Nettle stings can be neutralized with alkalis like the one found in dock leaves. 3) In neutron wastewater treatment, chemical neutralization methods are often applied to reduce the damage that an effluent may cause upon release to the

environment. For pH control, popular chemicals include calcium carbonate, calcium oxide, magnesium hydroxide, and sodium bicarbonate. The selection of an appropriate neutralization chemical depends on the particular application. Unique Feature of This Activity Simulation engages the learners by thrusting them into the learning experience. These kinds of interactions actively engage learners to analyze, synthesize, organize, and evaluate content and result in learners constructing their own knowledge. •

Students are engaged in active exploration and learning because they are aware of their existing ideas. For example, students know that gastric sufferer will take antacid to reduce the pain.

•

Students are able to visualize the process of neutralization. Simulations can represent real or imaginary situations. They allow users to study or try things that would be difficult or impossible to do in real life. There are some of the experiments are impossible to be carried on. By using simulations, students are able to study or try things that would be difficult or impossible to do in real life.

ENGAGE By assuming the boy in each picture is the same boy:

INCLUDEPICTURE "http://t2.gstatic.com/images?q=tbn:JwNmPCnhYAgJ1M:http://www.watchmojo.com/blogs/images/pizza.jpg" \* MERGEFORMATINET

A) What happened to the boy in the picture below?

B) How do the boy in the above picture feel? Why?

C) The boy is taking antacid, how does antacid work to relieve the boy’s stomach ache?

Answers

:

A) The boy in the above picture is eating pizza. B) The boy feels pain of stomach ache because he has eaten pizza. The human stomach produces hydrochloric acid, commonly known as "stomach acid." It is generated in the digestion process, but when the boy ate something requiring the stomach to work overtime in digesting it. For example, in digesting a pizza, the stomach may generate excess hydrochloric acid, and the result is "heartburn." When this happens, people often take antacids, which contain a base such as aluminum hydroxide (Al[OH] 3 ) or magnesium hydroxide (Mg[OH] 2 ). C) When the boy consumes an antacid, the reaction leads to the creation of a salt, but not the salt with which most people are familiar (NaCl). In any case, the antacid reacts with the stomach acid to produce a salt, as well as water, and thus the acid is neutralized.

EMPOWER 1. Students are allowed to perform their own titration without using any apparatus and materials by clicking the following link: http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/stoichio metry/acid_base.html 2. Students must follow a clearly numbered path through the steps of the experiment from selecting the acid, base, and indicator they will be using, to carefully adding drop by drop of the unknown titrant to the known acid or base.

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3. Now, students are ready to perform the titration. Carefully add small amounts of NaOH using the “slider” or the “drop wise” button until it just reach a color change.

4. Once a color change has accurately reached, calculate the unknown molarity of NaOH. The color change signifies that the point in the titration have been reached where the number of moles of OH- from the base, NaOH equals the number of moles of H+ from the acid, HCl forming water molecules and hence neutralizing the solution. The molarity of NaOH is calculated.

5. If the answer is correct, go on to see the titration curve by clicking on “Graph”. The graph will be sketched.

Questions

:

1. Why phenolphthalein indicator has pink color in basic solution and colorless in acidic solution? 2. Show the calculation to determine the molarity of unknown base (NaOH). Answers

:

1. In Equilibrium: HIn → H+ + InThe simplified reaction is: H+ + OH- → H2O As OH- ions are added, they are consumed by the excess of acid already in the beaker as expressed in the above equation. The hydroxide ions keep decreasing and the hydrogen ions increase, pH decreases. If the indicator equilibrium shifts left, In- ions decrease. Below pH 8.2 the indicator is colorless. As H+ ions are further increased and pH decreases to pH 4-5, the indicator equilibrium is affected and changes to the colorless HIn form. 2. Moles of HCl, n

= Molarity (mol L-1) × Volume (L) = 4.7675 × 10-3 mol

From the equation: HCl + NaOH → NaCl + H2O Moles of H+ are equal to moles of OH∴ Moles of NaOH = 4.7675 × 10-3 mol Molarity of NaOH

= Moles of NaOH (mol) Volume (L) = 0.2379 mol L-1

ENHANCE

A) Based on the picture above, explain what is the farm machine doing?

B) Now, the soil of the farm have white layer on the top. What do you think the white layer is? What is the purpose of the white layer? Answer

:

A) The farm machine is spreading white powder on the soil. B) The white layer is calcium carbonate (CaCO3 ) or limestone. When land formerly used for mining is reclaimed, the acidic water in the area must be neutralized, and the use of calcium oxide (CaO) as a base is one means of doing so. Acidic soil, too, can be neutralized by the introduction of calcium carbonate (CaCO 3 ) or limestone, along with magnesium carbonate (MgCO3 ). If soil is too basic, as for instance in areas where there has been too little precipitation, acid-like substances such as calcium sulfate or gypsum (SaSO4) can be used. In either case, neutralization promotes plant growth.