Chemical Reactions 2020 Arbuiso Chem Stuff to KEEP Chemical - - PDF document

Chemical Reactions 2020 Arbuiso Chem

Stuff to KEEP

Chemical Reactions BASICS

There are 5 simple reactions in this chemistry class (but more are coming later in the year). They are synthesis, decomposition, single replacement, double replacement, and combustion. You will be expected to recognize them with real chemistry symbols, or with "abstract" letters that stand in for actual chemicals. Examples for each are below. Each reaction has certain characteristics that make it different from the other types of reactions. Memorize these five, along with their example reactions so that you can draw upon this later in the year. Word equations describe the chemical reaction in words only. The "skeleton" equation is when you introduce the chemical symbols, all written with proper ion to ion - or atom to atom ratios - but the equation is NOT balanced. Balancing reactions takes practice. It converts the skeleton into proper final form, so that the law of conservation of matter is taken into consideration (the number of atoms or moles in the reactants equals the number of atoms or moles in the products). You are never allowed to have an unbalanced equation and be correct. Balanced equations include PHASE SYMBOLS, indicating what phase of matter (solid, liquid, gas, or aqueous solution) that the substance is in during that part of the reaction. Abbreviations are S, L, G, and AQ, put into subscript parenthesis.

EXAMPLES: H2O(L) for liquid water, H2O(S) for ice, or H2O(G) for steam. HCl(AQ) for hydrochloric acid - hydrogen chloride dissolved into water as a solution. Water cannot be aqueous by itself.

A reminder: ionic compounds are almost always solids at normal temperatures and pres-

• sure. All elements on the periodic table exist as single atoms - except for the HONClBrIF

twins, which are diatomic molecules. Molecular compounds can be gases or solids (you'll have to know what the compound actually is and think, or you have to ask). A few elements are liquids (mercury and bromine). In water ionic compounds will become aqueous solutions, or they won't - y

• u will have to check TABLE F (more on that later).

THE SYNTHESIS REACTION (1/5)

Defined, it is the reaction that puts smaller things together chemically into a larger chemical compound. The demo in class was the reaction of hydrogen combining with the oxygen in the air to form water. This reaction had hydrogen gas in a balloon, and a candle was used to both melt the balloon and to provide enough energy to start the

• reaction. The hydrogen combined with the oxygen in an explosion of fire and sound,

and the water formed was instantly vaporized by the heat. Reactions that give off heat are called EXOTHERMIC. This was an extremely fast synthesis that was also an exothermic reaction.

Word Equation: hydrogen plus oxygen yields water Skeleton Equation: H2 + O2 → H2O BALANCED EQUATION: 2H2(G) + O2(G) → 2H2O(G)

Other synthesis reactions include: iron rusting by combining with oxygen, magnesium oxide forming when magnesium gets hot enough to combine with oxygen in the air, or ammonia forming from hydrogen and nitrogen gases. Abstractly, this can be represented by: X + Y → XY Remember in class to protect your ears, and try not to blink too much or you miss this...

THE DECOMPOSITION REACTION (2/5)

This reaction that breaks up larger substances into two or more smaller substances. It is the reverse of synthesis. The demo in class was the reaction of hydrogen peroxide breaking down into water and oxygen gas. This particular reaction was also SO SLOW to watch you could not be sure it was

• happening. To speed it up the teacher added potassium iodide. That worked as a

catalyst: a substance that speeds up a chemical reaction but does not affect any the reaction any other way.

This reaction gave off a lot of heat, making it an EXOTHERMIC reaction. Oddly, that same amount of energy would have been given off without the catalyst, just so slowly that the heat would not be noticeable without a very accurate thermometer. The heat given off is a constant, the catalyst just made it all be given off in a very short period of time. We will learn much more about heats of reactions (ΔH) later in the year.

Word Equation: hydrogen peroxide decomposes into water & oxygen Skeleton Equation: H2O2 → H2O + O2 BALANCED EQUATION: 2H2O2(AQ) → 2H2O(L) + O2(G)

The hydrogen peroxide was a 27% solution dissolved into water. PURE hydrogen perox- ide could be a LIQUID, but ours was, technically speaking, a solution. Other decomposition reactions include: ammonia breaking down into hydrogen and ni- trogen, copper II carbonate (turquoise powder) breaking down into copper II oxide (black solid) and carbon dioxide (gas). Abstractly, this can be represented by: AB → A + B or, XY → X + Y

THE SINGLE REPLACEMENT REACTION (3/5)

To understand this reaction you need a bit more chemistry back-

• ground. When most ionic compounds are added to water they can

ionize, which means that the cation part and the anion part can separate and these ions literally float around dissolved in the water. They form an aqueous solution. We will learn more how this happens later in the year. Since these ions are now loose from each other, when a new substance is added into the solution, sometimes this new substance can push one of these ions out

• f solution and take its place.

This gives the reaction its name: the single replacement reaction. One substance replaces ONE PART of the ionic compound in

• solution. This only happens with an ionic compound in solution.

To further complicate things, depending upon what is in solution and what is added, the reaction can happen or it will not. Lucky for us TABLE J exists, to guide us. Table J is called the ACTIVITY SERIES. It lists in 2 columns, the activity level or better said: the REACTIVITY LEVEL of a lot

• f substances. A single replacement reaction has 3 parts, the single

substance that gets added into the aqueous solution (which has 2 parts itself). for example:

Mg(S) + HCl(AQ) →

the 3 parts are the Mg atom, the H cation and the Cl anion. If we look at Table J, we see that of these 3 parts, 2 of them are

• nly on one side of table J.

This always happens: 2 of the 3 parts are on one side of the table - on the left side in this reaction. Locate both Mg and H on the table. Since Mg is HIGHER UP on the table, that means that magnesium has a higher activity level, it would be able to bump out the hydrogen in a single replacement

• reaction. So...

the skeleton single replacement reaction would be: Mg + HCl → MgCl2 + H2

Metals Non Metals most active Li F2 Rb Cl2 K Br2 Cs I2 Ba Sr Ca Na Mg Al Ti Mn Zn Cr Fe Co Ni Sn Pb H* Cu Ag Au least active

*H is a non metal that acts like a metal in SR reactions

and the balanced chemical reaction would be: Mg(S) + 2HCl(AQ) → MgCl2(AQ) + H2(G)

Each Mg atom requires 2 molecules of the acid for the reaction to proceed.

NOTE: the table J exists ONLY TO LIST the activity levels. The reaction happens when the new single substance is HIGHER ON THE LIST because it has a higher activity level, not just because it is higher up on some list. Some single replacement reactions cannot occur, if the added single substance is LOWER

• n the list, meaning it does not have a high enough activity level.

For example, in class I put my GOLD WEDDING BAND into hydrochloric acid. Since Au is lower than the hydrogen, NO REACTION HAPPENED. Proper form for this is:

Au(S) + HCl(AQ) → X (no reaction)

We use Table J to determine whether or not a single replacement reaction will occur as written, or if it will not. We do not need to do every possible reaction since this table will give us the answer. In few occasions 2 of the 3 parts of the reaction will both be on the RIGHT SIDE OF THE TABLE. The same "rules" apply, if a single part is higher on the right side of table J it can replace itself into the solution. A "standard" example of this is:

Cl2(G) + 2NaBr(AQ) → 2NaCl(AQ) + Br2(G) Abstractly, SINGLE REPLACEMENT REACTIONS can be represented by...

A + BC → AC + B (when 2 of the three are on the LEFT side of Table J)

• r,

M + NP → no reaction

• r,

R + ST → SR + T (when 2 of the 3 are on the RIGHT side of Table J)

THE DOUBLE REPLACEMENT REACTION (4/5)

This reaction is what it sounds to be, a double switch by two different solutions of ionic

• compounds. The cations and anions are

separated from each other in the aqueous solutions as free ions floating around. When two different solutions of separated ions are combined, often the cations will switch anions in a double switch. This results in two new ionic compounds forming.

In our class we will assume that ALL double replacement reactions set up will go forward, and we'll use Table F to determine what precipitate is the evidence of reaction.

The original two solutions will be ionized into the water - another way to say that they are dissolve completely. When combined together, and when the cations switch their anions, sometimes the new compounds formed will also be soluble and remain dissolved. Other times these new compounds formed will be insoluble. These insoluble compounds will form precipitates which we will easily be able to see. The number of double replacement reactions is almost endless. Lucky for us that TABLE F exists to help us determine which kinds of ionic compounds will be soluble

• r insoluble. Using this table can be difficult at first but it is easy once you practice.

An example would be the reaction below: To use table F use in this reaction: the first compound is aqueous because according to the left side, all halides, which includes chlorides, are soluble except when combined to 3 certain cations of which calcium is not one. Therefore calcium chloride is soluble or an aqueous solution. The sodium carbonate is also soluble because we find carbonates on the right side where we see they are INSOLUBLE except when combined with GROUP 1 CATIONS which sodium is. It is therefore soluble or an aqueous solution as well. The word equation is... calcium chloride + sodium carbonate becomes calcium carbonate + sodium chloride

The balanced chemical reaction is... CaCl2(AQ) + Na2CO3(AQ) → CaCO3(S) --> 2NaCl(AQ)

The reactants are BOTH aqueous solutions. When the cations switch their anions, the products are insoluble calcium carbonate, and soluble sodium chloride. The precipitate CaCO3(S) would be EVIDENCE that the reaction happened. The calcium carbonate is INSOLUBLE because all carbonates are insoluble unless combined to a Group 1 cation or to ammonium ions, which in this case is not happening. Therefore the CaCO3 is INSOLUBLE or forms a SOLID PRECIPITATE. The sodium chloride is soluble, look at the table to be sure. If you are careful to look over the table, and READ IT SLOWLY, you can't go wrong with double replacement reactions. Just remember soluble = dissolves into aqueous solu- tion while insoluble = solid or a PRECIPITATE forms. Abstractly, visualize it this way: AB + XY → AY + XB (be sure to trade anions, do not mix up cations/anions with each other)

THE COMBUSTION REACTION (5/5)

This reaction is truly the easiest one. A compound that contains ONLY hydrogen and carbon must combine with oxygen to form ONLY carbon dioxide and water. It is PRETTY HARD to miss if you memorize that bold print. A HYDROCARBON is a compound that has ONLY hydrogen and carbon in it. Examples include methane (CH4), octane (C8H18), and butane (C4H10). The products must always be carbon dioxide and water. There can be NO OTHER

• PRODUCTS. This rule makes combustion easy to recognize. Combustion reactions

are always rather EXOTHERMIC, they give off lots of heat.

Word Equation: methane plus oxygen yields water and carbon dioxide Skeleton Equation: CH4 + O2 → H2O + CO2 BALANCED EQUATION: CH4(G) + 2O2(G) → 2H2O(G) + CO2(G)

Abstractly, here, X and Y represent subscripts of carbon and hydrogen in a hydrocarbon.

CxHy + O2 → H2O + CO2

At right a bunch of friends enjoy a camp fire, an excellent example of a hydrocarbon (the wood) rapidly combining with oxygen in the air, producing carbon dioxide and water (vapor), and excessive exothermic energy is released as light and heat. These five reactions all are BASIC reactions that will help further our study of matter and how it reacts. There are of course some asterisks out there waiting to surprise us. That is

• kay and we'll keep an eye out for them. There are several other reactions we will cover

later on, such as acid base neutralization reactions, and several nuclear reactions (which do not follow all the same laws, for instance the Law of Conservation of Matter). In nuclear reactions matter is converted into energy (E=mc2). Nuclear reactions are studied in chemistry, but are not part of the conservation of matter, or conservation of energy laws. They are NOT chemical equations by definition, matter and energy are

• ften out of “balance” that a normal chemical reaction or physical change must keep.

Reactions Notes

• 1. In a chemical reaction, sometimes ____________________________________ and sometimes

________________________________, and sometimes both happen. Every time a reaction occurs ___________________________________________________. These new substances have their own _______________________ that are not like the properties of the

• reactants. There are 5 of kinds of reactions that we learn about.

The first kind of reaction is called the __________________________________ REACTION. Sometimes it’s called a _________________________________________ reaction

• 2. In a synthesis reaction, ___________________________ reactants combine to form larger products.
• 3. The “ABSTRACT” is __________________________________
• 4. The _______________________________________________________________.

Let’s review some vocabulary so we can all talk properly

• 5. ______________________ are the substances that we _________________ with, they react together

and form the ____________________________________.

• 6. ________________________ are what we end up with.
• 7. In a synthesis reaction, we have 2 or more reactants that form into ___________________________.
• 8. It takes _______________ to start all chemical reactions.
• 9. If more energy comes out of the reaction with the products we call these EXOTHERMIC reactions.

If it requires more energy to start than comes out with the products, those reactions are called ENDOTHERMIC reactions.

• 10. A _____________________________________ describes the reaction with words, no symbols,

no numbers, as simply as possible.

• 11. Write out the word equation for the synthesis of water on the line.

_________________________________________________________________________________

• 12. The “skeleton” reaction for hydrogen and oxygen make water is

____________________ + ____________________ → ____________________

• 13. Skip this one!
• 14. Glinda the Good Witch from the Wizard of Oz tells us the best way to balance an equation. Her ad-

vice: ________________________________________________________________________________

• 15. Rewrite the skeleton reaction from above again. Then we’ll balance it.

____________________ + ____________________ → ____________________

• 16. There are the _______________________________________ of atoms on the reactant side as the

product side. Matter can’t be created or destroyed in a chemical reaction (or physical change).

• 17. Now re write the balanced chemical equation with the “energy” showing the balanced thermochemi-

cal equation. We will not need to redo this in steps again. ___________________ + ___________________ → ___________________ + __________

• 18. An important chemical adage: ________________________________________________________
• 19. It’s reverse is cool too: ______________________________________________________________

20. 21.

• 22. Sodium and chlorine make sodium chloride (balance this now)

_____________________________________________→_____________________________

• 23. Word equation: Iron + Oxygen synthesizes to iron III oxide (rust) write the skeleton, then balance it:

____________________ + ____________________ → ____________________

• 24. Word equation: Aluminum + sulfur synthesize into aluminum sulfide write skeleton, and balance.

____________________ + ____________________ → ____________________

• 25. Word equation: Potassium and bromine make potassium bromide write the skeleton, then balance it:

____________________ + ____________________ → ____________________

• 26. Balance these skeleton reactions, put the coefficients on the dashes. Do NOT write in any “ones”.

___C + ___O2 → ___CO ___Cu + ___O2 → ___Cu2O

___Zn + ___O2 → ___ZnO ___Al + ___O2 → ___Al2O3

• 27. Decomposition Reactions…

Example: Lead II oxide decomposes into lead and oxygen

___________________________→ ________________________ + _________________________

• 28. Decomposition reactions require _____________________________________ to break down into

___________________________________________________________________________________

• 29. Example of the Abstract: ________________________________________
• 30. Word equation for our demonstration: hydrogen peroxide decomposes into water & oxygen gas
• 31. Skeleton ________________________→ _______________________ + ___________________
• 32. Balance it now.
• 33. How do we make chemical reactions go faster? We can add a _____________________________
• 34. Show where you add the catalyst in the equation above, put it where it belongs.
• 35. The…
• 36. With no catalyst, a reaction will __________________________________

With a catalyst the same reaction will occur, just __________________________________ The catalyst is ________ ___ _________________________!!!

• 37. Magnesium nitride decomposes into magnesium & nitrogen. Write the skeleton, then balance it:

__________________________→ ________________________ + ___________________

• 38. Magnesium carbonate decomposes into carbon dioxide & magnesium oxide. Write skeleton + balance

__________________________→ ________________________ + ___________________

• 39. Iron (II) oxide decomposes. Write the skeleton, then balance it:

__________________________→ ________________________ + ___________________

• 40. Ammonia gas decomposes. Write the skeleton, then balance it:

__________________________→ ________________________ + ___________________

• 41. Hydrogen monochloride gas decomposes. Write the skeleton, then balance it:

__________________________→ ________________________ + ___________________

• 42. Dinitrogen Pentoxide Decomposes into nitrogen and oxygen. Write the skeleton, then balance it:

__________________________→ ________________________ + ___________________

• 43. Single Replacement reactions (SR) start with you…
• 44. Aqueous means _______________________________________________________.

We will only use ionic compounds dissolved in water for these reactions.

• 45. Ionic compounds have _______________ _______________ and ___________ _____________

that dissolve into water, AND they will _________________ this way: Example:

• 46. The salt disappears & dissolves. At the atomic level, NaCl separates into positive & negative ions

which swim in the water. This is a _________________________________ : _____ → ____

• 47. Water is _________________________________________________________________________.
• 48. Another ionic compound that dissolves and ionizes in water is SILVER NITRATE. Let’s put some

atoms of COPPER into that solution, which is a nice single replacement reaction set up. ____________ + ______________________ → ______________________ + ____________

• 49. The copper…
• 50. Since the nitrate anion basically “hangs out”

we call it the _________________________________________

• 51. A single replacement reaction always has ____________ parts,

the ____________________, the _____________________ and the __________________________.

• 52. 2 of these 3 are ALWAYS on one side of table J or the other side of table J.

In this reaction, see that both COPPER and SILVER are on the LEFT SIDE of Table J.

• 53. Copper is ______________________________ than silver, so it ________________ the silver out
• f solution and takes the copper’s place in the solution.
• 54. Copper is MORE REACTIVE than silver, so it will bump the silver out of solution, and takes it’s

place dancing with the nitrate ion. Draw the reaction with the arrows to show that.

• 55. Single Replacement Reaction #2 Magnesium metal into HYDROCHLORIC ACID

But first let’s look at table K, the acids. Show how table salt ionizes in water ________________________________________________

• 56. Show how HCl(G) ionizes in water _____________________________________________________
• 57. Show the skeleton for Magnesium metal into Hydrochloric Acid, then balance the equation

____________ + ______________________ → ______________________ + ____________

• 58. State what happened (copy the blue text in the slide show)
• 59. Draw the diagram

• 60. Au(S) + HCl(AQ) → _________________
• 61. Why is there no reaction? ___________________________________________________________

Balance these three SR reactions

• 62. ___Mg(S)+ ___Zn(NO3)2(AQ) → ____________________________ + ________________
• 63. ___Na(S) + ___Sn(NO3)2(AQ) → ____________________________ + ________________
• 64. ___Cl2(G)+ ___KBr(AQ) → ____________________________ + ________________
• 65. That last one is special!
• 66. ___Zn(S)+ ___H2SO4(AQ) → ____________________________ + ________________
• 67. ___Li(S) + ___Co(NO3)3(AQ) → ____________________________ + ________________
• 68. ___Au(S)+ ___KCl(AQ) → ____________________________ + ________________

Double Replacement Reactions

• 69. It takes ___________________________________ solutions to start a double replacement reaction.
• 70. The ________________________________________________________________with each other.
• 71. In the abstract: _______________________________→___________________________________
• 72. The reaction occurs if a ____________________________________ forms in the products.
• 73. If no precipitate forms, a _________________________ formed, but no chemical reaction happened.

Copper (II) nitrate solution + Lithium chromate solutions combine…

• 74. Write out the reactant side of this skeleton reaction to start. Write small! (underline just the cations)

___________________+ _____________________→___________________+ ___________________ Switch the cations/anions; FIX the products; Balance the equation; Check Table F to decide AQ or S. What is table F? Let’s look before we can finish this up. Label the tops of the four columns as shown.

• 75. Table F tells us if an ionic compound will be…
• 76. The second product here, the CuCO3 is _______________________ or _______________________
• 77. Make sure your #74 is PERFECTLY balanced and has FOUR phase symbols, that are correct now.
• 78. 2nd Word equation: Sodium chloride + lead (II) acetate solutions combine…

(finish the word equation) ...into _________________________________ and __________________________________ 79—80. Balance this word equation, with phase symbols now.

• 81. Write the IONS and FORMULAS. Are these AQ or S in water?
• 82. Balance this: Potassium phosphate + calcium chloride solutions combine into… write out the

symbols, and then switch em’, fix ‘em, and table F ‘em! Write small, ALL ON ONE LINE! ___________________+ ____________________→___________________+ ____________________

• 83. ____BaCl2(AQ) + ___RbOH(AQ) → ______________________+____________________

What happened here? Compound IONS FORMULA AQ or S ? Silver chloride Ag+1 Cl-1 AgCl S Magnesium nitrate Sodium hydroxide Strontium sulfate Calcium nitrate Barium acetate Aluminum chlorate Lead (II) bromide Lithium sulfide Ammonium chromate Barium sulfate

Combustion Reactions

• 84. Combustion reactions require a _________________________ to combine rapidly with

_______________________, forming ______________ + _______________and lots of ener- gy. There is little challenge recognizing these reactions, the only difference is the TYPE of hydrocarbon you start with. They always combine with oxygen to form CO2 and H2O and energy. .

• 85. Hydrocarbon: a compound made of _____________________+________________________ only.
• 86. Every single combustion reaction looks like this:
• 87. Hydrocarbon examples gases ___________________ liquids____________________ solid _____
• 88. First practice example: the simplest of all hydrocarbons, methane combusts.

We write out the skeleton reaction, then balance it… _________________ + __________________ → __________________ + ____________________

• 89. Balance these two in a row. Put coefficients on the dashes, do NOT write ones.

____C2H6(G) + _____O2(G) → ___________________ + ____________________ ____C3H8(G) + ____O2(G) → __________________ + _____________________

• 90. Sometimes we find ourselves BURNING (combusting) an OXYGENATED HYDROCARBON.

• 91. Combustion reactions require a hydrocarbon (or oxygenated hydrocarbon) to combine with oxygen,

and it ALWAYS FORMS INTO _____________________________and _____________________________ + HEAT

• 92. Word Equation: Methanol + oxygen yields carbon dioxide & water

(Methanol is an alcohol, but NOT the “alcohol” in wine and beer) WRITE SKELETON on the line __________________ + __________________ → __________________ + ___________________

• 93. Balance this equation.
• 94. Butane (C4H10) combusts. WRITE THE SKELETON, balance this equation.

__________________ + __________________ → __________________ + ___________________

• 95. Octane (C8H18) combusts. WRITE THE SKELETON, balance this equation.

__________________ + __________________ → __________________ + ___________________

Review of All Chemical Reactions…

• 96. Write out two balanced chemical equations with phase symbols for these two word equations.

Phosphorous + chlorine gas form into phosphorous pentachloride gas. _________________ + ______________________ → ______________________ Manganese VII oxide forms manganese and oxygen gas ______________________ → ______________________ + _____________________

Write out the balanced chemical equations for these possible SINGLE REPLACEMENT REACTIONS

• 97. Sodium goes into silver nitrate solution

____________ + ______________________ → ______________________ + ____________

• 98. Bromine is added to lithium iodide solution

____________ + ______________________ → ______________________ + ____________

• 99. Tin is added to barium nitrate solution

____________ + ______________________ → ______________________ + ____________

• 100. Lithium nitrate and potassium chloride solutions are poured together

_________________ + __________________ → __________________ + ____________________

• 101. Lead (II) hydrogen carbonate and Cobalt (III) sulfate solutions are poured together

_________________ + __________________ → __________________ + ____________________ Write out the balanced chemical equations for these COMBUSTION REACTIONS

• 102. Hexane combusts

______C6H14 + __________________ → __________________ + ____________________

• 103. Propanol combusts () this is a type of alcohol.

______C3H5OH + __________________ → __________________ + __________________

• 104. In complete combustion, only ___________________ forms with water.
• 105. In an incomplete combustion reaction, where there is INSUFFICIENT oxygen to react normally,

the formation of _____________________________ is possible. This carbon monoxide is poison, breathing it can cause death. There are MANY different reactions with the formation of CO(G).