FINAL EXAM- Reactions and reaction types

Question 1

Law of conservation of mass

Answer 1

atoms are neither created nor destroyed in a chemical change

Question 2

Composition

Answer 2

aka synthesis. Many reactants⇒one product. Opposite of decomposition

Question 3

types of composition

Answer 3

• 2 types
• Metals with Halogens- Ex. Na(s)+Cl2(g)⇒2NaCl(s)
• With oxides (end in O)- Ex. CaO(s)+H2O(l)⇒Ca(OH)2(s)

Question 4

Decomposition

Answer 4

One reactant⇒many products

Question 5

Types of decomposition

Answer 5

• 6 types
  a) Electrolysis
• Use electricity to break the bond
• Ex. H2O(l)⇒2H2(g)+O2(g)
  b) Binary Decompositon
• Take elements in compound and break them apart
• Ex. 2HgO(s)⇒2Hg(l)+O2(g)
  c) Metal Carbonate breaks to form metal oxide+carbondioxide
• Ex. CaCO3(s)⇒(Δ above arrow) CaO(s)+CO2(g)
  d) Metal hydroxide to form metal + water
• Ex. Ca(OH)2(s)⇒(Δ above arrow)CaO(s)=+H2O(l)
  e) Metal chlorate to form a metal chloride and oxygen
• Ex. 2KClO3(s)⇒2KCl(s)+3O2(g)
  f) Tertiary acid to form an oxide and water
• Ex. H2CO3⇒⇐CO2(g)+H2O(l)
• ⇒⇐=could go both ways (not specific to this type of reaction, just in general)

Question 6

Single replacement

Answer 6

When there’s an element and a compound that form an element and a compound and the element replaces its like element in the compound, activity series permitted.

• X+AB⇒AX+B
• X+AB⇒XB+A
• Both above are cation replacements
• Y+AB⇒AY+B
• Above is anion replacement
• Cation replacement- metal replaces metal
• Anion replacement- nonmetal replaces nonmetal
• Use activity series of elements to determine if an element can replace or not
• Ex. Li+NiO⇒Li2O+2Ni
• Metals fight metals and nonmetals fight nonmetals
• Metal and nonmetal always together
• Whichever element is higher on the list wins the fight
• Ex. BaS+Mg⇒NR (no reaction) because Ba is higher on the list so he wins the fight and gets to keep S
• Ex. F2+NaBr⇒NaF+Br2 because F is higher on the list and wins the fight. F2 and Br2 because they are diatomic elements

Question 7

Double replacement

Answer 7

• 2 compounds for both reactants and products, peaceful switch with no fight.
• AB+XY⇒AY+XB
• Positive/metal is always written first
• Ex. 2NaCl(aq)+Pb(NO3)2(aq)⇒2NaNO3(aq)+PbCl2(s)
• Compound for both reactants and products

Question 8

Neutralization

Answer 8

aka water forming.

• Type of Double replacement
• Acid+Base⇒Salt+water
• HX+YOH⇒YX + HOH
• Acids start with H (except water) and bases end in OH
• In chemistry, salt is all ionic compounds except acids and base
• Ex. HCl(aq)+KOH(aq)⇒KCl(aq)+HOH(l)
• Ex. 2H(NO)3+Ca(OH)2(aq)⇒2HOH(l)+Ca(NO3)2(aq)

Question 9

Combustion

Answer 9

• Complete Combustion
• Hydrocarbon (H/C/O) + (excess) Oxygen ⇒(Δ above arrow) Carbon Dioxide+water
• Ex. C2H5OH+O2⇒CO2+H2O
• Incomplete combustion
• Hydrocarbon+(limited)O2⇒CO+H2O (carbon monoxide) or C+H2O(carbon)

Question 10

Solubility rules

Answer 10

Chart that allows you to determine if a compound is soluble in water

Question 11

Products

Answer 11

A substance that forms in a chemical reaction

Question 12

Reactants

Answer 12

a substance or molecule that participates in a chemical reaction

Question 13

Coefficients

Answer 13

(big number in front of the substance symbol)= number of particles in the substance, used to balance.

Question 14

Endothermic reaction

Answer 14

Energy+reactants⇒products=endothermic

Question 15

Exothermic reaction

Answer 15

Reactants⇒Products+Energy=exothermic

Question 16

Symbols in reactions

Answer 16

• Reactants yield sign ⇒ products
• Plus sign separates reactants/products
• S=Solid
• L=Liquid
• G=Glas
• Aq=aqueous- dissolved in water- water doesn’t take place in the reaction
• Coefficient- (big number in front of the substance symbol)= number of particles in the substance
• Subscripts- used to write the formula corrects so that we have a net charge of zero
• Catalyst- speeds up the reaction without changing its structure
• up arrow indicates g, don’t need to put it in parenthesis
• Sometimes down is used instead of (s) for a precipitate, don’t put in parenthesis
• Δ=add heat for reaction to occur

Question 17

Know how to balance reactions from words and symbols

Answer 17

• Coefficients are added in front of molecules, formula units, or atoms to balance the total number of each atoms in the equation.
• Ex. 6Li+Sr3N2⇒2Li3N+3Sr
• Ex. 2C8H18+25O2⇒16CO2+18H2O
• Originally C8H18+25/2 O2⇒8CO2+9H2O
• In this case, everything was doubled
• When writing compound, make sure metal/+ goes first, then nonmetal/-

Question 18

Know how to determine reaction type

Answer 18

• Many reactions ⇒one product= synthesis
• One reactant⇒many products=Decomposition
• Element+compound⇒ Element+compound=single replacement
• 2 compounds for both reactants and products=double replacement
• Acid+Base⇒Salt+water= water forming/neutralization
• Hydrocarbon (H/C/O) + (excess) Oxygen ⇒(Δ above arrow) Carbon Dioxide+water= combustion

Question 19

Predict the products in a reaction

Answer 19

• Determine reaction type from reactants
• Follow pattern to determine products
• Write formulas for products correctly (use subscripts)
• Balance equation using coefficients

Question 20

Know how to indicate an exothermic or endothermic reaction in a balanced equation

Answer 20

• Indicate an exothermic reaction by having energy as one of your products
• Indicate an endothermic reaction by having energy as one of your reactants

Question 21

Determining phase of matter

Answer 21

• All ionic compounds are solids at room temperate unless there’s water around and they are soluble
• Ionic= cation (+) + Anion (-)
• All metals besides mercury are solids at room temperature. Ex. Li(s)
• Not all nonmetals are gases, just the ones on Mrs. Howards period table. Ex. O2(g)
• Nobel gases are always gases. Ex. Ne(g)
• Always check chart when possible to determine solubility