Chem 017 Lab Exercise 3: Chemical Reactions PDF

1 School Year 2024-2025 CHEM 017 LAB EXERCISE 3: Chemical Reactions COURSE Code/ Title : CHEM 017– GENERAL CHEMISTRY MODULE TITLE : CHEMICAL REACTIONS NAME OF ST...

1 School Year 2024-2025 CHEM 017 LAB EXERCISE 3: Chemical Reactions COURSE Code/ Title : CHEM 017– GENERAL CHEMISTRY MODULE TITLE : CHEMICAL REACTIONS NAME OF STUDENT : SECTION/ GROUP NO. : DATE SUBMITTED : MODULE OBJECTIVES: After the end of the lesson, the student should be able to: 1. Differentiate the types of chemical formulas and give examples for each. 2. Be able to give the chemical formula of some inorganic compounds. 3. Demonstrate chemical reactions using household products and predict their balanced chemical equations. 4. Watch films of chemical reactions and be able to synthesize and give reflections on the videos. 1 Chem017 Lab Module 3  2 COURSE MATERIALS A. CHEMICAL FORMULAS A.1 Types of Chemical Formulas. A chemical formula is an expression involving chemical symbols and numerical. The symbols represents the different types of elements present (i.e. composition) in the compound while the numerical indicates the number of atoms in one molecule of a compound, when it is written as a subscript after the symbol of the element. Example is H2 which show that it contains two atoms of hydrogen; H2SO4 shows that the chemical formula contains two atoms of hydrogen, one atom of sulphur and four atoms of oxygen. There are basically three types of chemical formulas namely empirical, molecular and structural formulas. EMPIRICAL FORMULA: This is the simplest formula of a compound that shows the simplest whole number ratio of atoms of different elements present in a compound. Hence the empirical formula of the compound C2H4O2 is CH2O, where the integer multiplier is 2. Normally, the results of chemical analysis are expressed as percentage by mass of each constituent element, so to know the identity of the compound the empirical formula will be calculated from the percentage composition. Calculation of the empirical formular of the compound entails first determining the relative number of moles of atoms of each element present in the given mass of the compound. Thereafter, the number of moles of each element is then divided by the smallest number of the mole present. MOLECULAR FORMULA: This is a formula of a compound that shows the exact (actual) number of atoms of different element present in a compound. The molecular formula is given by Molecular Formula = Empirical formula X integer multiplier Molecular formula = n (Empirical formula) Sometimes, empirical formula and molecular formula can be the same. This is when the molecular formula cannot be reduced further. Examples includes NH3 (ammonia), CaCO3 (calcium trioxocarbonate (IV), H2O (water) CO2 (carbon(IV)oxide) etc. STRUCTURAL FORMULA: - The structural formula shows the way that atoms are joined together in a molecule. Knowledge of the structural formula of compound is important in the study of chemistry because some compounds may have the same molecular formula and empirical formula and the only thing that will show that the compounds are different is their structural formula. As an illustration, Butanol and ethyl ether have the same empirical and molecular formula as C4H10O. The only thing that differentiates the two and gives both their respective unique set of properties is the structural formula. 2 Chem017 Lab Module 3  3 A.2 Predicting Formulas from Valencies. Valency is the number of electrons an atom can lose, gain or share to acquire an octet or duplet electronic configuration. The formulas of compounds can be deduced from the valences of component elements or radicals using the following rules Rule 1: Write the symbols of the component elements or radicals Rule 2: Place the valences of each elements or radical below the respective element or radical Rule 3: Interchange the valences and write them as subscript immediately after the respective symbols of the atoms. Rule 4: Write the formula of the compound by first writing the metals followed by the non-metals Note: When the subscript is one, it is disregarded and when all the subscripts can divide through, they are further reduced. Example 1. Example 2. B. CHEMICAL REACTIONS are the processes by which chemicals interact to form new chemicals with different compositions. Simply stated, a chemical reaction is the process where reactants are transformed into products. How chemicals react is dictated by the chemical properties of the element or compound- the ways in which a compound or element undergoes changes in composition. A chemical reaction is typically represented by a chemical equation, which represents the change from reactants to products. The left hand side of the equation represents the reactants, while the right hand side represents the products. A typical chemical reaction is written with stoichiometric coefficients, which show the relative amounts of products and reactants involved in the reaction. Each compound is followed by a parenthetical note of the compound’s state of 2: (l) for liquid, (s) for solid, (g) for gas. The symbol (aq) is also commonly used in order to represent an aqueous solution, in which compounds are dissolved in water. A reaction might take the following form: A(aq)+B(g) → C(s)+D(l)A(aq)+B(g) → C(s)+D(l) 3 Chem017 Lab Module 3  4 In the above example, AA and BB, known as the reactants, reacted to form CC and DD, the products. To write an accurate chemical equation, two things must occur: 1. Each product and reactant must be written using its chemical formula, e.g., H2H2 2. The number of atoms of each element must be equal on both sides of the equation. Coefficients are used in front of the chemical formulas in order to help balance the number of atoms, e.g., 2Mg+O2 → 2MgO Types of Chemical Reactions (1) Precipitation, or double-replacement reaction A reaction that occurs when aqueous solutions of anions (negatively charged ions) and cations (positively charged ions) combine to form a compound that is insoluble is known as precipitation. The insoluble solid is called the precipitate, and the remaining liquid is called the supernate. See Figure 1. Figure 1. Precipitation reaction. Real life example: The white precipitate formed by acid rain on a marble statue: CaCO3(aq)+H2SO4(aq) → CaSO4(s)+H2O(l)+CO2(g) 4 Chem017 Lab Module 3  5 (2) Acid-base, or Neutralization reaction A neutralization reaction occurs when an acid and base are mixed together. An acid is a substance that produces H+ ions in solution, whereas a base is a substance that that produces OH- ions in solution. A typical acid-base reaction will produce an ionic compound called a salt and water. A typical acid-base reaction is the reaction between hydrochloric acid and sodium hydroxide. This reaction is represented by the equation: HCl(aq)+NaOH(aq) → NaCl(aq)+H2O(l) In this reaction, HCl is the acid, NaOH is the base, and NaCl is the salt. Real life example: Baking soda reacts with vinegar is a neutralization reaction. (3) Oxidation-Reduction (Redox) Reactions A redox reaction occurs when the oxidation number of atoms involved in the reaction are changed. Oxidation is the process by which an atom’s oxidation number is increased, and reduction is the process by which an atom’s oxidation number is decreased. If the oxidation states of any elements in a reaction change, the reaction is an oxidation-reduction reaction. An atom that undergoes oxidation is called the reducing agent, and the atom that undergoes reduction is called the oxidizing agent. An example of a redox reaction is the reaction between hydrogen gas and fluorine gas: H2(g)+F2(g) → 2HF(g) In this reaction, hydrogen is oxidized from an oxidation state of 0 to +1, and is thus the reducing agent. Fluorine is reduced from 0 to -1, and is thus the oxidizing agent. Figure 2: In redox reaction of Equation 4, a H2 molecule donates electrons to F2 resulting in two HF molecules. Real life example: The cut surface of an apple turns brownish after exposed to the air for a while. 5 Chem017 Lab Module 3  6 (4) Synthesis Reactions A synthesis reaction occurs when one or more compounds combines to form a complex compound. The simplest equation of synthesis reaction is illustrated below. Figure 3. Synthesis reaction An example of such a reaction is the reaction of silver with oxygen gas to form silver oxide: 2Ag(s)+O2(g) → 2AgO(s) Real life example: Hydrogen gas is burned in air (reacts with oxygen) to form water: 2H2(g)+O2(g) → 2H2O(l) (5) Decomposition Reactions A decomposition reaction is the opposite of a synthesis reaction. During a decomposition reaction, a more complex compound breaks down into multiple simpler compounds. A classic example of this type of reaction is the decomposition of hydrogen peroxide into oxygen and hydrogen gas: H2O2(l) → H2(g)+O2(g) Figure 4: The molecule AB is decomposing into A and B 6 Chem017 Lab Module 3  7 (6) Single Replacement Reactions A type of oxidation-reduction reaction in which an element in a compound is replaced by another element. Figure 5. Single Replacement reaction as shown in the example below. This is also a redox reaction. Cu(s)+AgNO3(aq) → Ag(s)+Cu(NO3)2(aq) LABORATORY EXERCISE 4: Chemical Reactions Objectives: The students should be able to: 1. Conduct experiments using household chemicals. 2. Predict the chemical equation in the reaction of household chemicals. 3. Balance the chemical equations involved in the chemical reactions Materials & Methods: Materials Needed: Raw Egg, Coke (cold bottle), Match sticks, Muriatic Acid, Liquid Sosa, Agua Oxigenada (blue 20 volumes), Aluminum foil, liquid detergent, Powdered colored dye ( Diobos), Baking Soda, Powdered Yeasts. Combine the following household chemicals / specimens, observe, take a picture/video and give the chemical reactions involved. (1) Egg Experiment  Raw egg soaked in a glass of Vinegar for 24 hrs (2) Lighting a matchstick (3) Cold bottle of Coke + 1 tsp salt (4) Muriatic Acid (placed in small glass bottle) + 1 tsp Baking Soda (5) Liquid Sosa + Hot water  mix in glass bowl + crumpled pieces of aluminum foils 7 Chem017 Lab Module 3  8 Experiment Observations Balanced Chemical Reaction involved Type of Chemical Reaction Picture of the set-up during the Involved chemical reaction (1) Egg Experiment (2) Matchstick (3) Coke & Salt (4) Muriatic Acid & Baking Soda (5) Liquid Sosa & Aluminum foil 8 Chem017 Lab Module 3  9 Discussion of Experiments: Film Analysis: Watching a Video Watch the 2 films: (1) “Types of Chemical Ractions” https://youtu.be/WWJQpuv9ElE (2) “ Black Snake Chemical Reaction” https://youtu.be/NERwRanxWXQ 9 Chem017 Lab Module 3  10 (1)Types of Chemical Ractions (2) Black Snake Chemical Reaction Film Assessment Be able to answer the following questions for each film: 1. Summarize the films. 2. For Film no.1, enumerate, differentiate & give examples of the types of chemical reactions mentioned. 3. For Film no.2, compare the ingredients used in the experiment and which among the chemicals gave the best result. 4. What is the importance of knowing chemical reactions to engineers? Feedback: A. Make a Reflection/ Insights for the experiment B. Evaluate your groupmates using the Rubrics below: Chem 001: GENERAL Chemistry Rubrics Name of Leader (1): Names of Members: (2-4) Group No. Date/Time: 1 2 3 4 CRITERIA Novice (0-1 pt) Accomplished (2-3) Excellent (4-5) RELEVANCE The topic is briefly defined and The topic is defined but not clearly understood The topic is identified, clearly understood and is remotely related to the theme. and is still relevant to the theme. highly relevant to the theme. CONTENT Displays an incomplete understanding Displays a complete and accurate understanding Demonstrates a thorough understanding of the of the important concepts and of the important concepts or generalizations. important concepts or generalizations and includes generalizations and has some notable new insights misconceptions. TECHNICAL VALIDITY Ideas may not be focused or The main idea is evident,but the organizational Ideas are clearly organized, & ORGANIZATION developed; the main purpose is not structure may need to be strengthened; ideas may developed, and supported to clear. not always flow smoothly. achieve a clear purpose. INNOVATIVENESS Visuals go well with the report, but Satisfactory use of visuals and manner of Uses outstanding and appropriate medium and there are too few and the report seems presentation, although at times, some are material for the visual aids. "text-heavy". distracting. 10 Chem017 Lab Module 3  11 PREPAREDNESS The discussion is difficult to hear or The presentation is appealing, but may contain The presentation is appealing and easy to follow. It understand and the flow of information unclear information. Some appeal to audience draws in the audience and keeps their attention. is confusing. and distractors kept to a minimum. Lecturer is completely prepared. TIME MANAGEMENT Became on-line late & started the Took time to set up the report Started & ended the report on time report late. TOTAL /30 Learning Resources: 1. eBook o Baruch, 2020. Chemistry: Laboratory Instructions & Exercises https://www.baruch.cuny.edu/wsas/academics/natural_science/Chemistry1000LaboratoryNotes.htm o Muniratu, Maliki. 2019. Introductory Chemistry I. Edo University. https://www.edouniversity.edu.ng/oer/lecturenotes/chm_111_introductory_chemistry_i_lecture_notes_20182019 o Roussel, Marc. 2020. General Chemistry http://people.uleth.ca/~roussel/C1000/ 2. On-line video o Types of Chemical Ractions” https://youtu.be/WWJQpuv9ElE o “ Black Snake Chemical Reaction” https://youtu.be/NERwRanxWXQ 3. Scanned Reference Books o Guzman, R and RM G Puzman-Genuino. 2018. Environmental Science: Towards a Sustainable Earth. QC, Phil. Vibal Group Inc. (scanned 2020). o FEU GenChem Committee. 2015. Guide Notes and Learning Module in General Chemistry. Far Eastern University, Mla. 4. Additional References 11 Chem017 Lab Module 3  12 12 Chem017 Lab Module 3