1 / 35

Technical Science Introduction to Chemistry

Technical Science Introduction to Chemistry. Chemical Equations. Chemical Equations. In this tutorial you will… Analyze a Chemical Equation Prove a Chemical Equation is Balanced Explain Reasons for Balancing Equations Explore Common Chemical Reactions. 1 of 5.

viveka
Télécharger la présentation

Technical Science Introduction to Chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Technical Science Introduction to Chemistry Chemical Equations

  2. Chemical Equations • In this tutorial you will… • Analyze a Chemical Equation • Prove a Chemical Equation is Balanced • Explain Reasons for Balancing Equations • Explore Common Chemical Reactions

  3. 1 of 5 Analyze a Chemical Equation Home • One of the main functions of chemistry is to determine what will happen when substances react. • A chemical equation is the method used to express what happens during a chemical reaction. • The chemical equation below outlines a familiar chemical reaction. What is this telling you? 2Na + Cl2 2NaCl • A chemical equation is really just a recipe. • It tells you the amounts of specific ingredients that are required to make a certain amount of a product.

  4. 2 of 5 Analyze a Chemical Equation • Let’s take a closer look at that chemical equation. 2Na + Cl2 2NaCl Reactants Products First, you should notice that the equation is broken into two parts with an arrow.The arrow represents the chemical reaction. The “ingredients” on the left side of the equation are called the Reactants The “results” on the right side of the equation are called the Products

  5. 3 of 5 Analyze a Chemical Equation • Identify the reactants and the products in the following reactions. N2 + 3H2 2NH3 BaCO3 BaO + CO2 MnO2 + 4HCl  MnCl2 + Cl2 + 2H2O Reactants Products

  6. 4 of 5 Analyze a Chemical Equation • Let’s take another look at that chemical equation. 2Na + Cl2 2NaCl Coefficients Subscripts The subscripts in this equation tell us… Na is in elemental form.2 Cl atoms are bonded to form a molecule of chlorine gas.1 Na is bonded to 1 Cl to make a molecule of sodium chloride. Coefficients tell the number of atoms or molecules that are required for the reaction. Coefficients are the amounts of the reactants and products. The coefficients in this equation tell us…Two sodium atoms will react with One chlorine molecule to produce Two molecules of sodium chloride. The small numbers following the chemical symbols are called Subscripts.(Subscripts of one are not written out.) Subscripts tell the number of atoms that are bonded together to makea single molecule of a substance. They determine the substance itself. You probably noticed the numbers associated with chemical formulas for the reactants and the products. The large numbers in front of the formulas are called Coefficients. (Coefficients of one are not written out.)

  7. 5 of 5 Analyze a Chemical Equation Home • What do the chemical equations below tell you? N2 + 3H2 2NH3 (NH3 is Ammonia) 2MgO + Si  2Mg + SiO2 1 molecule of nitrogen gas reacts with 3 molecules of hydrogen gas to form 2 molecules of ammonia. Nitrogen and hydrogen molecules are each formed from 2 atoms bonded together. Ammonia is formed from 1 N atom bonded to 3 H atoms. 2 molecules of Magnesium Oxide (each with 1Mg bonded to 1 O) react with 1 atom of silicon to form 2 atoms of magnesium and 1 molecule of silicon dioxide (having 1 Si bonded to 2 O)

  8. 1 of 6 Prove a ChemicalEquation is Balanced Home Remember: coefficients of 1 are not written out. • An equation must be balanced to be useful. • The equation below is not balanced. Can you see what is missing? 2 1 2 Na + Cl2 NaCl • There are no coefficients in the equation above. • Coefficients determine the amounts of reactant and product. • The amounts of reactant and product are correct when the coefficients make the equation balance.

  9. 2 of 6 Prove a Chemical Equation is Balanced • Prove the equation is balanced. 2Na + Cl2 2NaCl Na 2 2 Cl 2 2 This gives a total of two sodium atoms and two chlorine atoms on the product side. The Coefficient of 2 and the lack of subscripts, tells us there are 2 molecules of sodium chloride. Each molecule has 1 Na and 1 Cl. This reaction is balanced because there are same number and types of atoms on each side. The lack of a subscript and the coefficient of 2 on sodium, tells us that there are 2 Na atoms on the reactant side. Third: Count the number of atoms of each type on the product side.You will consider both coefficients & subscripts The subscript of 2 and the lack of a coefficient on chlorine, tells us that there is one molecule of chlorine that contains 2 Cl atoms. First: Identify the all of the different elements that are involved in this reaction.There are 2 types of atoms: Sodium & Chlorine We need to keep track of types and numbers of atoms on each side of the equation. So…Let’s get organized by creating a table Remember, a balanced chemical equation has the same type and number of atoms on both the reactant and product sides. Second: Count the number of atoms of each type on the reactant side.You will consider both coefficients & subscripts

  10. 3 of 6 Prove a Chemical Equation is Balanced • Prove the equation is balanced. MnO2 + 4HCl  MnCl2 + Cl2 + 2H2O Mn 1 1 O 2 2 H 4 4 Cl 4 2 4 This reaction is balanced because there are same number and types of atoms on each side. Chlorine shows up in two products MnCl2 & Cl2. Cl2 tells us there is 1 molecule of chlorine gas with 2 Cl atoms bonded together. There are a total of 4 chlorine atoms on the product side of the equation; 2 from the MnCl2 and 2 from the Cl2. MnCl2 tells us there is one molecule that has 1 manganese bonded to 2 chlorines.So, there is 1Mn atom and 2 Cl atoms. 2H2O tells us that there are two molecules each having one oxygen bonded to two hydrogens.So there are four hydrogen and two Oxygen 4HCl tells us that there are four molecules each having one hydrogen bonded to one chlorine.So there are four hydrogen and four chlorine. MnO2 tells us that there is one molecule of this compound and it has one manganese bonded to two oxygens. Second: Count the number of atoms of each type on the reactant side.You will consider both coefficients & subscripts First: Identify the all of the different elements that are involved in this reaction.There are 4 types of atoms: Mn, O, H, & Cl We need to keep track of types and numbers of atoms on each side of the equation. So…Let’s get organized by creating a table Third: Count the number of atoms of each type on the product side.You will consider both coefficients & subscripts Remember, a balanced chemical equation has the same type and number of atoms on both the reactant and product sides.

  11. 4 of 6 Prove a Chemical Equation is Balanced • Prove the following reaction is balanced. 2NO + 2CO  N2 + 2CO2 N 2 2 4 O 4 2 2 C

  12. 5 of 6 Prove a Chemical Equation is Balanced • Prove the following reaction is balanced. P4O10 + 4HNO3  4HPO3 + 2N2O5 P 4 4 22 O 22 4 4 H N 4 4

  13. 6 of 6 Prove a Chemical Equation is Balanced Home • Prove the following reaction is balanced. C6H12O6 + 6O2  6CO2 + 6H2O C 6 6 12 H 12 18 18 O

  14. 1 of 5 Explain Reasons forBalancing Equations Home • You know that a reaction is balanced when the coefficients make the number and type of atoms on each side of the equation equal. 2Na + Cl2 2NaCl • You can also prove whether a reaction is balanced. • But why is it so important to balance an equation? • Why wouldn’t you want to write the equation like this… Na + Cl2 NaCl • There are at least three reasons why it is important to balance a chemical reaction.

  15. Cl Na Na Cl Cl Cl 2 of 5 Explain Reasons forBalancing Equations • Look at the unbalanced equation below. Na + Cl2 NaCl 2 2 Na Na The Law of Conservation of Matter.This law states that matter can not be created or destroyed only changed in form. The unbalanced equation above suggests that an atom of chlorine just disappeared.This is against the law. This means if we start with two atoms of chlorine we must end with two atoms of chlorine. Where did that other chlorine go?It has to go somewhere. It can’t just disappear.This leads us to a very important law in chemistry. When the proper coefficients are in place and the equation is balanced, all the atoms can be accounted for. Now we are following The Law of Conservation of Matter. Notice there are two chlorine atoms on the reactant side but only 1 chlorine on the product side.

  16. O O O H H H H H H 3 of 5 Explain Reasons forBalancing Equations • Look at the partially balanced equation below. 2Fe + 3H2O  Fe2O3 + H2 3 Fe Fe O-Fe-O-Fe-O H-H H-H H-H Notice in this partially balanced equation that the iron and the oxygen are balanced. However, the hydrogens from water on the reactant side are not accounted for on the product side.Where did those hydrogen atoms go? As it turns out, the hydrogen atoms bonded together to form another product: Hydrogen Gas (H2) If a chemical equation is not properly balanced, you may miss a potential product. Hydrogen gas is odorless and colorless but explosive.That’s not a product you would want to overlook. What coefficient in front of the H2would make this equation balance?

  17. 4 of 5 Explain Reasons forBalancing Equations • What does the unbalanced reaction below tell you? Na + Cl2 NaCl 2 2 Na Na Cl-Cl Na-Cl Na-Cl This reaction, as written, tells you that sodium atoms (Na) react with chlorine gas molecules (Cl2) to form molecules of sodium chloride (NaCl) We know the ingredients and products but we don’t know how much of each is needed. The amounts of each substance are determined by the coefficients that are assigned when the equation is balanced. Balancing the equation tell us how much of each reactant is required and how much of each product will be produced. Remember, chemical equations are recipes. They tell the amounts of the ingredients required and the amounts of product you can expect. An unbalanced equation is like a recipe that tells you all the ingredients but doesn’t tell you how much of each one to use

  18. 5 of 5 Explain Reasons forBalancing Equations Home • Why is it important to work with a balanced chemical equation? • If an equation isn’t balanced, it implies that atoms suddenly appear or disappear. This goes against the Law of Conservation of Matter • If an equation isn’t balanced, you may miss a product that is not easily observed. • An equation is a chemical recipe. If it isn’t balanced, it is like a recipe that doesn’t include any amounts. It would be useless to try to make something from such a recipe.

  19. 1 of 16 Explore Common Chemical Reactions Home • A chemical reaction is a recipe that lists amounts and type of both reactants and products. • In this section you will analyze common chemical reactions. • The goal is to give you the background information necessary to determine the type of product when given the reactants. • There are seven of these reactions. You have already had experience with some of them. • The following slides will present each of these common chemical reactions.

  20. 2 of 16 Explore Common Chemical Reactions • Salt Formation Metal + Nonmetal  Salt Na + Cl2 NaCl 2 2 4 Fe + O2 Fe2O3 3 2 In the specific example above, Iron reacts with Oxygen to form Iron III Oxide. Which is commonly known as rust. Most metal objects must be protected from oxygen so this reaction doesn’t occur. This is one reason for painting metal objects. Metals combine with nonmetals to form salts. A specific example is shown above with sodium metal reacting with chlorine gas. There is a special case of this type of reaction.Metals react with Oxygen (a nonmetal) to form a Metal Oxide (a salt) Metals combining with oxygen is also called corrosion or oxidation. This reaction can be a costly one because degrades metal objects.

  21. 3 of 16 Explore Common Chemical Reactions • What product would be formed from the reactants listed below. Mg + O2 2 2 MgO Metal + Nonmetal  Salt (Oxygen) (Metal Oxide) Mg (magnesium) is a metal. O2 (oxygen) is a nonmetal.Metals combine with nonmetals to form salts. In this case, the salt that forms will be a metal oxide because the nonmetal is oxygen. The product is Magnesium Oxide (MgO)Mg takes on a +2 charge & O is –2.So one Magnesium balances one Oxygen. The chemical equation is balancedwith the coefficients shown above.

  22. 4 of 16 Explore Common Chemical Reactions • Base Formation Metal Oxide + Water  Base Na2O + H2O  NaOH You now know that a metal oxide is a salt.It is composed of a metal bonded to oxygen.You also know water is H2O. Remember a base is type of compound that has a metal bonded to the Hydroxide Ion (OH –1).Here, the metal is sodium (Na+1) The base that is formed is Sodium Hydroxide.Na has a +1 charge & OH has a –1 charge so the formula is NaOH. (one Na with one OH) Bases represent an important class of compounds. When you hear the term caustic or alkaline, it is probably in reference to a base.

  23. 5 of 16 Explore Common Chemical Reactions • What product would be formed from the reactants listed below. CaO + H2O  Ca(OH)2 Metal Oxide + Water  Base CaO (calcium oxide) is a Metal Oxide. H2O is Water.Metal Oxides combine with water to form bases. The product is Calcium Hydroxide (Ca(OH)2)Ca takes on a +2 charge & OH is –1.So one Calcium balances two Hydroxide ions. The chemical equation is balancedas it is shown above.

  24. 6 of 16 Explore Common Chemical Reactions • Acid Formation NonmetalCompound + Water  Acid SO3 + H2O  H2SO4 Nonmetal compounds are two or more nonmetals covalently bonded.You also know water is H2O. Remember an acid is type of compound that has a Hydrogen ion(s) bonded to a nonmetal.Here, the nonmetal is the sulfur trioxide (SO3) The acid that is formed is Sulfuric Acid.H has a +1 charge & SO4 has a –2 charge. The formula is H2SO4. (two H+ with one SO4-2) Acids are another important class of compounds. You have heard of various acids; stomach acid, acid rain, battery acid, acetic acid (vinegar), citric acid (in fruits), ascorbic acid (vitamin C), etc

  25. 7 of 16 Explore Common Chemical Reactions • What product would be formed from the reactants listed below. CO2 + H2O  H2CO3 NonmetalCompound + Water  Acid CO2 (carbon dioxide) is a nonmetal compound. H2O is Water.Nonmetal compounds combine with water to form acids. The product is Carbonic Acid (H2CO3)H takes on a +1 charge & CO3 is –2.So two Hydrogens balance one Carbonate ion. The chemical equation is balancedas it is shown above.

  26. 8 of 16 Explore Common Chemical Reactions • Neutralization Acid + Base  Salt + Water HCl + NaOH NaCl +HOH You probably also noticed that in this reaction the pairs atoms traded partners. The H from the acid bonded to the OH from the base.The Na from the base bonded to the Cl from the acid. The pairs of atom replaced each other to form two new substances.This type of reaction is sometimes called a double replacement reaction. A salt is a metal bonded to a nonmetal. The metal is the Na+1 from the base.The nonmetal is the Cl-1 from the acid. These ions form the salt NaCl An acid releases hydrogen H+1 ions.A base releases hydroxide OH-1 ions.The acid in this case is HCl. The base is NaOH. The water forms from the remaining ions. The H+1 (from the acid) bonds to the OH-1 (from the base). This makes H-OH or H2O (water). The H+ ions of acids and the OH- ions of bases make them very reactive compounds.But when they react together, the H+ ions and the OH- ions bond tightly to each other. This forms water which is very stable.The acid and the base “neutralize” each other.This reaction is often called neutralization. When you take an antacid for an upset stomach, what you are really doing is neutralizing your stomach acid with a base (the antacid).

  27. 9 of 16 Explore Common Chemical Reactions • What product would be formed from the reactants listed below. HCl + Mg(OH)2 2 MgCl2 + HOH 2 Acid + Base  Salt + Water One product, the salt, is Magnesium Chloride (MgCl2)Mg takes on a +2 charge & Cl is –1.So, one Magnesium balances two Chlorines The other product, the water, is H-OHThe H (from the acid) takes on a +1 charge.The OH (from the base ) has a –1 charge.So, water is HOH or H2O. The chemical equation is balancedwith the coefficients shown above. HCl is an acid. Mg(OH)2 is a base. Acids react with bases to form a Salt and Water.

  28. 10 of 16 Explore Common Chemical Reactions • Metal Plating 1st Metal + Salt  2nd Metal + Salt Zn + CuSO4  Cu + ZnSO4 You can see the original metal (the zinc), took the place of the copper in the salt. We started with Copper II Sulfate & ended with Zinc Sulfate. The zinc replaced the copper. This type of reaction is often called a single replacement reaction. This type of reaction is very common.It is found in batteries and metal plating.However, it will only occur if the original metal is more reactive than the metal in the salt. Zinc is more reactive than copper so this reaction will take place.If copper metal was placed in a solution of zinc sulfate, nothing would happen. The second metal (product) comes from the metal portion of the original salt. The metal is in solid elemental form.The salt is dissolved water as ionsThe metal here is Zn. The salt is CuSO4. The salt that is produced is formed from the original metal and the nonmetal portion of the original salt.

  29. 11 of 16 Explore Common Chemical Reactions • What product would be formed from the reactants listed below. (Magnesium is more reactive than Silver) Mg + AgNO3 2 Ag 2 + Mg(NO3)2 Metal 1 + Salt  Metal 2 + Salt The other product, the salt, is Mg(NO3)2The magnesium is now an ion Mg+2and with two nitrate ions NO3-1forms a new salt. (Magnesium Nitrate) One product, the metal, is Silver (Ag)The silver was replaced by the magnesium. Mg donated its e- becoming a Mg+2 ion.The Ag+1 ions accepted the e- and went back to elemental form. The chemical equation is balancedwith the coefficients shown above. Mg is a metal. Ag(NO3)2 is a salt. Metals can react with salts producing a new salt by replacing the metal.

  30. 12 of 16 Explore Common Chemical Reactions • Combustion Carbon Dioxide Organic Compound + Water + Oxygen  CH4 + O2 2  CO2 + H2O 2 The chemical equation is balancedwith the coefficients shown above. This is a reaction that you encounter daily. The reaction of organic compounds with oxygen to produce carbon dioxide and water is called combustion. One product is Carbon Dioxide (CO2)The other product is Water (H2O) Another word for combustion is burning.This reaction allows us to release energy from organic fuel sources. These fuels may be the gasoline in your car, the natural gas that heats your home, coal, oil or the food you eat to power your body.The basic reaction is the same for each. Organic compounds contain carbon.In this case, it is methane gas (CH4) Oxygen is simply Oxygen Gas (O2)

  31. 13 of 16 Explore Common Chemical Reactions • What product would be formed from the reactants listed below. C3H8 + O2 5 3 CO2 + H2O 4 Carbon Dioxide OrganicCompound + Oxygen  + Water There is an additional product in combustion reactions and that is energy.The production of energy is the reason we burn these fuels. The chemical equation is balancedwith the coefficients shown above. The two products in any combustion reaction are always Carbon Dioxide and Water. C3H8 (propane) is an organic compound.It reacts with oxygen in a combustion reaction to form carbon dioxide and water.

  32. 14 of 16 Explore Common Chemical Reactions • Polymerization Monomer + Monomer  Polymer C2H3Cl + C2H3Cl  -[C2H3Cl]-[C2H3Cl]- The polymer that is formed in this case is a chain of vinyl chloride molecules.It is called Polyvinyl Chloride (PVC). The process of polymerization is used to make create synthetic substances like plastics, nylon, styrofoam, etc. A monomer is a relatively small molecule.The monomers in this example are vinyl chloride molecules C2H3Cl Small molecules are bonded together to form larger molecules. The groups of monomers are called polymers. The process of putting small molecules (monomers) together to form larger molecules (polymers) is called polymerization. Polymerization is also used by living things.Proteins are polymers of amino acids. Starch and cellulose are polymers of simple sugars.

  33. 15 of 16 Explore Common Chemical Reactions • What product would be formed from the reactants listed below. C2F4 + C2F4  -[C2F4]-[C2F4]- Polymer(Teflon) Monomer(Tetrafluoroethylene) + Monomer  The product is Teflon.It is a polymer of the small C2F4 monomers. C2F4 are monomers. Monomers combine to form Polymers.

  34. 16 of 16 Name Salts with Multivalent Metals Home • Write the general reactants and products Metal + Nonmetal  Salt Metal Oxide + Water  Base Nonmetal Compound + Water  Acid Acid + Base  Salt + Water Metal 1 + Salt  Metal 2 + Salt Organic + Oxygen  Carbon + WaterCompound Dioxide Monomer + Monomer  Polymer

  35. Technical Science Introduction to Chemistry You have Completed Chemical Equations Created by John W. Pluemer

More Related