Test 8- Reactions Flashcards Preview

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Flashcards in Test 8- Reactions Deck (74):
1

Chemical reaction

A process by which one or more substances are changed into one or more different substances

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Substance

Atom (element), Formula Unit (ionic compound), or molecule (covalent bonded compound)

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Atom

Element all by itself

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Formula Unit

ionic compounds- metal and nonmetal

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Molecule

covalent compound=2 nonmetals

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To represent a chemical reaction

use an equation- can be with words or symbols

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Reactants yield sign

⇒ products

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Plus sign

separates reactants/products

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Phases of matter

in parenthesis after substance symbols
- S= Solid
- L= liquid
- G= gas
- Aq= aqueous

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Aqueous

dissolved in water- water doesn’t take place in the reaction

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Coefficient

(big number in front of the substance symbol)= number of particles in the substance

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Subscripts

used to write the formula correctly so that we have a net charge of zero

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catalyst

- speeds up the reaction without changing its structure
- represented above the yield sign

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up arrow indicates

g, don’t need to put it in parenthesis

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Δ=

add heat for reaction to occur

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Down arrow indicates

s for a precipitate, don’t put in parenthesis

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Endothermic

Energy+reactants⇒products

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Exothermic

Reactants⇒Products+Energy

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Exothermic

Reactants⇒Products+Energy

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Reaction types

1. Synthesis or Composition
2. Decomposition
3. Single Replacement/Single Displacement
4. Double Replacement/Double Displacement/Ionic
5. Water forming/Neutralization
6. Combustion

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Synthesis or Composition

- Many reactants⇒one product
- Opposite of synthesis/composition

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Types of Synthesis or Composition

2 types:
a) Metals with Halogens (all diatomic)
Ex. Na(s)+Cl2(g)⇒2NaCl(s)

b) With oxides (end in O)
Ex. CaO(s)+H2O(l)⇒Ca(OH)2(s)

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Decomposition

One reactant⇒many products

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Types of Decomposition

6 Types:
1. Electrolysis
2. Binary
3. Metal carbonate
4. Metal hydroxide
5. Metal chlorate
6. Tertiary acid

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First type of decomposition

Electrolysis
- Use electricity to break the bond
- Ex. H2O(l)⇒2H2(g)+O2(g)

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Second type of decomposition

Binary
- Take elements in compound and break them apart
- Ex. 2HgO(s)⇒2Hg(l)+O2(g)

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Third type of decomposition

Metal Carbonate breaks to form metal oxide+carbondioxide
- Ex. CaCO3(s)⇒(Δ above arrow) CaO(s)+CO2(g)

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Fourth type of decomposition

Metal hydroxide to form metal + water
- Ex. Ca(OH)2(s)⇒(Δ above arrow)CaO(s)=+H2O(l)

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Fifth type of decomposition

Metal chlorate to form a metal chloride and oxygen
- Ex. 2KClO3(s)⇒2KCl(s)+3O2(g)

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Sixth type of decomposition

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)

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Single Replacement/Single Displacement

- X+AB⇒AX+B
- X+AB⇒XB+A

- Y+AB⇒AY+B

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Cation replacement

metal replaces metal
- X+AB⇒AX+B
- X+AB⇒XB+A

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Anion replacement

nonmetal replaces nonmetal
- Y+AB⇒AY+B

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How to write a compound

- First element in compound=metal
- Second element in compound=nonmetal

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Activity series to determine

If can 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

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Double Replacement

- aka Double Displacement/Ionic
- 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

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Water forming

- Aka neutralization
- Type of Double replacement
- Acid+Base⇒Salt+water
- HX+YOH⇒YX + HOH
- Ex. HCl(aq)+KOH(aq)⇒KCl(aq)+HOH(l)
- Ex. 2H(NO)3+Ca(OH)2(aq)⇒2HOH(l)+Ca(NO3)2(aq)

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Acids

Start with H (except water)

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Bases

End in OH

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In chemistry, salt is

all ionic compounds except acids and bases

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Complete combustion

- Hydrocarbon (H/C/O) + (excess) Oxygen ⇒(Δ above arrow) Carbon Dioxide+water
- Ex. C2H5OH+O2⇒CO2+H2O

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Incomplete combustion

- Hydrocarbon+(limited)O2⇒CO+H2O (carbon monoxide) or C+H2O(carbon)

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Law of conseration of matter (mass)

atoms are neither created nor destroyed in a chemical change

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Coefficients are added

in front of molecules, formula units, or atoms to balance the total number of each atoms in the equation.

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If fraction

double everything

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Steps to predicting products

1. Determine reaction type from reactants
2. Follow pattern to determine products
3. Write formulas for products correctly (use subscripts)
4. Balance equation using coefficients

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Determine phase of matter rules

1. All ionic compounds are solids at room temperate unless there’s water around and they are soluble
- Ionic= cation (+) + Anion (-)
2. All metals besides mercury are solids at room temperature
3. Not all nonmetals are gases, just the ones on Mrs. Howards period table
4. For covalent bonds, look at the shape and determine the polarity and IMF
5. Nobel gases are always gases
6. Always check chart when possible to determine solubility
7. Assume room temperature

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Determine phase of matter rules

1. All ionic compounds are solids at room temperate unless there’s water around and they are soluble
- Ionic= cation (+) + Anion (-)
2. All metals besides mercury are solids at room temperature
3. Not all nonmetals are gases, just the ones on Mrs. Howards period table
4. For covalent bonds, look at the shape and determine the polarity and IMF
5. Nobel gases are always gases
6. Always check chart when possible to determine solubility
7. Assume room temperature

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Rate of reaction

- The speed of different chemical reactions varies hugely.
- Some reactions are very fast and others are very slow.
- Ex. Rusting is slow, baking is fast/medium, and explosions are really fast

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The speed of a reaction is called

the rate of reaction

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Molecules/Atoms/FU have to collide

with each other in the right orientation for a reaction to occur.

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Reactions take place when

particles collide with a certain amount of energy

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activation energy

The minimum amount of energy needed for the particles to react and it is different for each reaction.

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The rate of a reaction depends on three things:

1. The frequency of collisions between particles
2. The energy with which the particles collide
3. Orientation of particles when they collide

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If particles collide with less energy than the activation energy

they will not react. The particles will just bounce off each other.

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Reactions do not proceed at a steady rate

- They start off at a certain speed, then get slower and slower until they stop.
- Ex. When you first open soda, it bubbles a lot and gradually slows down

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As the reaction progresses, the concentration of reactants decrease

- This reduces the frequency of collisions between particles and so the reaction slows down.

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Reading reaction profile

- Go from reactants to products to tell if its endothermic or exothermic
- Energy difference from reaction to peak of reaction profile is the activation energy
- Activation energy= minimum energy to make a reaction happen
- As reactanats gain energy, particles get closer together

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Exothermic Reaction profile

- Curve with reactants higher than products.
- Reactants have more energy than products so its exothermic

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Endothermic Reaction profile

- Curve with products higher that reaction
- Products higher than reactants so its endothermic

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How rate of reaction can be measured

- Measuring the rate of reaction means measuring the change in the amount of a reactant or the amount of a product
- To set it up, you can put the reaction in a flask, put a stopper in with a glass tube leading to a gas syringe and you can measure the amount of gas being released and the rate of reaction.
- You can also measure that has being released by weighing the reaction every so often.

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Graphing rate of reaction

- Y=reaction rate
- X=substrate concentrate
- Starts low and grows until it levels off
- Line levels out because there is no more products being made because there are no more reactants to react and create more products
- Slope of graph=initial rate of reaction at that time
- Rate of reaction=y/x(slope)

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Effect of temperature on rate

- Temperature is the average of all the energies
- If you raise the temperature (red line), there are more particles to react (shaded part to the right of line), and therefore a faster reaction
- If you lower the temperature (blue line) there are less particles to react (only a little shaded to the right of the line) and therefore a slower reaction

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Effect of temperature on Rate of reaction

- The higher the temperature, the fast the rate of a reaction
- In many reactions, a rise in temperature of 10C causes the rate of reaction to approximately double
- At a higher temperature, particles have more energy. This means they move faster and are more likely to collide with other particles
- When particles collide, they do so with more energy, and so the number of successful collisions increases.
- Ex. Car batteries need to be replaced more often in hot weather because the increased temperature causes the reaction that generates the electric current to proceed faster.
- Reaching activation energy is a bigger factor than collision rate
- Raising the temperature is the best way to increase reaction rate

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Effect of pressure on rate of reaction

- As pressure increase, the space in which the has particles are moving becomes smaller
- The gas particles become closer together, increasing the frequency of collisions. This means that the particles are more likely to react.
- Only works for gas reactions

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Effect of concentration on rate or reaction

- The higher the concentration of a dissolved reactant, the faster the rate of a reaction
- At a higher concentration, there are more particles in the same amount of space.
- This means that the particles are more likely to collide and therefore more likely to react.
- Can achieve this by adding more solute or decreasing solvent

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Effect of surface area on rate of reaction

- Any reaction involving a solid can only take place at the surface of the solid.
- If the solid is split into several pieces, the surface area increases.
- This means that there is an increased area for the reactant particles to collide with.
- The smaller the pieces, the larger the surface area.
- This means more collisions and a greater chance of reaction.

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Catalysts info

- Catalysts are substances that change the rate of a reaction without being used up in the reaction
- Catalysts never produce more product- they just produce the same amount more quickly

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Effect of catalysts on rate of reaction

- Most catalysts work by lowering the reactions activation energy as shown above and allowing a faster reaction
- They also work by making sure at least one reactant is in the right orientation for collision

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Everyday catalysts

1. Nickel as a catalyst for margarine
2. Iron from ammonium from nitrogen and hydrogen
3. Platinum in the converters of car exhaust.

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Catalysts are important for industry because

1. Products can be made quickly, saving time and money
2. Catalysts reduce the need for high temperatures, saving fuel and reducing pollution

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Catalysts in the body

Catalysts are also essential for living cells. Biological catalysts found in the body are special types of protein called enzymes

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Extra credit question

9, 12, 3, 9, 6

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How Activation series of elements works

- a series of elements that have similar properties and that are arranged in descending order of chemical activity; examples of activity series include metals and halogens.
- A list of elements organized according to the ease with which the elements undergo certain chemical reactions
- For metals, greater activity means greater ease of loss of electrons to form positive ions
- For nonmetals, greater activity means a greater ease of gain of electrons, to form negative ions