Module 04 : Reactions Flashcards
The reaction 2NO(g) + O2(g) → 2NO2(g) is a synthesis reaction. (2 points)
True
False
True
What is true of synthesis and decomposition reactions? (4 points)
- Synthesis reactions require more energy than decomposition reactions.
- Synthesis reactions produce more products than decomposition reactions.
- Synthesis reactions are the opposite of decomposition reactions.
- Synthesis reactions have fewer reactants than decomposition reactions.
3. Synthesis reactions are the opposite of decomposition reactions.
A synthesis reaction can be identified because it only has pure elements on the left side of the arrow and compounds on the right side of the arrow. (2 points)
- True
- False
False
Which chemical equation correctly represents the synthesis of calcium sulfite from calcium oxide and sulfur dioxide? (4 points)
- CaSO3(s) → CaO(s) + SO2(g)
- CaSO3(s) + O2(g) → CaO(s) + SO2(g)
- CaO(s) + SO2(g) → CaSO3(s)
- CaO(s) + SO2(g) → CaSO3(s) + O2(g)
3. CaO(s) + SO2(g) → CaSO3(s)
Which of the following is a synthesis reaction? (4 points)
- AgNO3 + NaCl → AgCl + NaNO3
- CH4 + O2 → CO2 + H2O
- SO3 + H2O → H2SO4
- Cu + AgNO3 → Ag + CuNO3
3. SO3 + H2O → H2SO4
An unbalanced chemical equation is shown:
H2O2 → 2H2O + O2
Which of the following statements explains why the equation is not balanced? (4 points)
- Two H2O2 molecules should decompose to form the given products.
- Four H2O2 molecules should decompose to form the given products.
- Two H2O2 molecules should undergo a synthesis reaction to form the given products.
- Four H2O2 molecules should undergo a synthesis reaction to form the given products.
1. Two H2O2 molecules should decompose to form the given products.
Define a Synthesis Reaction:
Synthesis Reaction: reaction two+ reactants combine to form one product
A + B → AB
Define Decomposition reaction:
Decomposition Reaction: Single compound reactant to form more than one product
AB → A + B
What are the components of Chemical equations?
A chemical reaction involves bonds being broken and formed as atoms rearrange to make new substances
Reactant: Initial substance before chemical change
Product: New substance after a chemical change
Define Chemical Change:
- Left to right
- Represented in chemical formulas
- The phase of each substance indicated in subscripts
(s) for solid, (l) for liquid, and (g) for gas
(aq) → aqueous solution → compounds dissolved in water to forma solution
Define the Law of Conservation of Mass:
Law of Conservation of Mass: Mass cannot be created or destroyed within a closed system
- In chemical equations: equal number of elements on both sides of the equation
- in experiments the initial weight/volume will be the same total at the end
Fill in the blank with the correct number to balance the equation: 4Cr + 3O2 → Cr2O3. (Enter only a whole number.) (3 points)
2
For the reaction VCl2 + Cl2 → VCl5, what are the reactants, products, and correct coefficients in the balanced equation? (3 points)
- Reactants: 2VCl2 and 3Cl2; product: 2VCl5
- Reactants: 2VCl2 and 1Cl2; product: 2VCl5
- Products: 1VCl2 and 2Cl2; reactant: 1VCl5
- Products: 2VCl2 and 1Cl2; reactant: 2VCl5
1. Reactants: 2VCl2 and 3Cl2; product: 2VCl5
Which of the following laboratory procedures best illustrates the law of conservation of mass? (Assume the product of the reaction includes the mass of any unused reactants.) (3 points)
- Calculating the number of atoms in 11 g of Na
- Using 250 g of impure Cu to obtain 200 g of pure Cu
- Heating 32 g of S and 56 g of Fe to produce 88 g of FeS
- Burning 2.4 g of Mg in an open crucible to produce 2 g of MgO
3. Heating 32 g of S and 56 g of Fe to produce 88 g of FeS
A chemical equation is shown:
Al + O2 → Al2O3
According to the law of conservation of mass, how many atoms of oxygen exist in the products of this reaction? (3 points)
- 6
- 5
- 3
- 2
- 6
When methane, CH4, is combusted, it produces carbon dioxide, CO2, according to the unbalanced equation: CH4 + O2 → CO2 + H2O.
Write the balanced equation for this reaction, and explain how it is possible for 10 grams of methane fuel to burn and emit 27 grams of carbon dioxide. Discuss whether or not this reaction obeys the law of conservation of mass. (5 points)
In the equation above, there are 4 hydrogen atoms on the left side and only two on the right; therefore, a coefficient of 2 has to be added before the compound H20. Now the equation is as follows: CH4 + O2 → CO2 + 2H2O. On the right side of the equation, there are 4 oxygen atoms now and only two on the left, so a coefficient of two has to be added to the left oxygen atom to make it equal to four: CH4 + 2O2 → CO2 + 2H2O. There is 1 carbon atom on the left and the right, so the element is balanced. Since, according to the Law of Conservation of Mass, the energy/amount of atoms has to stay the same, the balanced equation is CH4 + 2O2 → CO2 + 2H2O.
All reactions have to obey the Law of Conservation of Mass, so even when the transfer of matter is not clear; therefore, the reaction above has to make logical sense in some way or another. Even though the methane in the initial reactants weighed less than the CO2, the diatomic oxygen atom also contributed to the reactants’ weight, so the carbon chemically reacted with the oxygen, which is why it weighs more in the product than the reactant.
Define Single Replacement Reactions:
- What is the formula
- and the components of the formula
Reaction one element replaces a similar element in a compound
A + BC → AC + B
- A → neutral element
- BC → ionic compound
- Positive ion A replaces positive ion B in ionic compound
Define Double Replacement Reactions:
- What is the formula
- and the components of the formula
Reaction in which ions of two compounds exchange places in aqueous solution to form two new compounds
AB + CD → AD + CB
- A, B, C, D → reactants represent ions
A & C: positive ions
B & D negative ions
- AD & CB → ionic or molecular compounds
What are the reactants and products of Single Replacement Reactions?
Reactants: element + compound
Product: different element + different compound
What are the reactants and products of double replacement reactions?
Reactants: two compounds
Product: two different compounds
products are typical:
- precipitate or solid
- gas (bubbles)
- water
What is the “Active Series?”
- list elements in reactivity
- SRR: when the replacement element more reactive than the element it tries to replace
What are:
- Beginning Reactions
- Ionic Breakdown
- Balanced Equations
Beginning Reactions:
- positive ions of reactants switch positions to create a product
Ionic Breakdown:
- ions trade places
- combine form neutral compounds
Balanced Equations:
- coefficients used balance overall equation
What are the observable changes in Double Reaction Equations?
- Insoluble Product
- Molecular Product
- Predipitate
Define Aqueous solutions:
the reaction only noticeable when a change is appearance or state occurs
Define Acid-Base Reactions:
Process of neutralization of acid using a base → Acid-Base Reaction or Neutralization Reaction
- double displacement reaction
*
What is a salt, acid-based reaction?
ionic compound formed by reaction of acid and base
Define Acid:
substance is hydrogen ion donor when dissolved in water/reaction
Most acids: H+
Define Base:
- Substance hydrogen acceptor in the reaction
- Produces hydroxide ions when dissolved in water
Most Bases: OH
The reaction 2NO(g) + O2(g) → 2NO2(g) is a synthesis reaction. (2 points)
True or False
True
What is true of synthesis and decomposition reactions? (4 points)
- Synthesis reactions require more energy than decomposition reactions.
- Synthesis reactions produce more products than decomposition reactions.
- Synthesis reactions are the opposite of decomposition reactions.
- Synthesis reactions have fewer reactants than decomposition reactions.
3. Synthesis reactions are the opposite of decomposition reactions.
A synthesis reaction can be identified because it only has pure elements on the left side of the arrow and compounds on the right side of the arrow. (2 points)
True or False
False
Which chemical equation correctly represents the synthesis of calcium sulfite from calcium oxide and sulfur dioxide? (4 points)
- CaSO3(s) → CaO(s) + SO2(g)
- CaSO3(s) + O2(g) → CaO(s) + SO2(g)
- CaO(s) + SO2(g) → CaSO3(s)
- CaO(s) + SO2(g) → CaSO3(s) + O2(g)
3. CaO(s) + SO2(g) → CaSO3(s)
Which of the following is a synthesis reaction? (4 points)
- AgNO3 + NaCl → AgCl + NaNO3
- CH4 + O2 → CO2 + H2O
- SO3 + H2O → H2SO4
- Cu + AgNO3 → Ag + CuNO3
3. SO3 + H2O → H2SO4
An unbalanced chemical equation is shown:
H2O2 → 2H2O + O2
Which of the following statements explains why the equation is not balanced? (4 points)
- Two H2O2molecules should decompose to form the given products.
- Four H2O2molecules should decompose to form the given products.
- Two H2O2molecules should undergo a synthesis reaction to form the given products.
- Four H2O2molecules should undergo a synthesis reaction to form the given products.
1. Two H2O2molecules should decompose to form the given products
A single replacement reaction is a reaction in which one element replaces a similar element within a compound. (2 points)
True
False
True
Which of the following equations has the correct products and is balanced correctly for a reaction between Na3PO4 and KOH? (4 points)
- Na3PO4 + 3KOH → 3NaOH + K3PO4, because K retains the same charge throughout the reaction
- Na3PO4 + 3KOH → Na3OH + KPO4, because K increases in charge from 1+ to 3+ when it is replaced
- Na3PO4+ KOH → 3NaOH + K3PO4, because K retains the same charge throughout the reaction
- Na3PO4+ KOH → Na3OH + K3PO4, because K increases in charge from 1+ to 3+ when it is replaced
1. Na3PO4 + 3KOH → 3NaOH + K3PO4, because K retains the same charge throughout the reaction
When I2 and FeCl2 are mixed together, iodine (I) cannot replace chlorine (Cl) in the compound because iodine is lower on the periodic table. (2 points)
True or False
True
Which of the following is a double replacement reaction? (4 points)
- Ca(OH)2 + H2SO4 → CaSO4 + 2H2O
- CH4 + 2O2 → CO2 + 2H2O
- 8Fe + S8 → 8FeS
- Zn + H2SO4 → ZnSO4 + H2
1. Ca(OH)2 + H2SO4 → CaSO4 + 2H2O
A double replacement reaction is a reaction in which one element replaces a similar element within a compound. (2 points)
True or False
False
When HNO3 and Au are mixed together, what do you expect to happen, and why? (4 points)
- No reaction, because Au is above H on the activity series and they cannot react
- No reaction, because Au is lower on the activity series and cannot replace H
- They form Au(NO3)2 and H2, because Au is more reactive and able to replace H
- They form Au(NO3)2 and H2, because they trade places in a double replacement reaction
2.
No reaction, because Au is lower on the activity series and cannot replace H
The table shows the nature of the reactants and products formed in a certain type of chemical reaction.
Nature of Reactants and Products
Reactants Products Ionic compound + Ionic compound Ionic compound + Ionic compound
Which of the following is true about this type of chemical reaction? (4 points)
- It is a single replacement reaction, and all four compounds are different.
- It is a double replacement reaction, and all four compounds are different.
- It is a single replacement reaction, and each compound has the same set of ions.
- It is a double replacement reaction, and each compound has the same set of ions.
2. It is a double replacement reaction, and all four compounds are different.
Potassium hydroxide (KOH) reacts with sulfuric acid (H2SO4) to produce potassium sulfate (K2SO4) and water.
What best describes this reaction? (4 points)
- A single replacement reaction occurs because potassium ions bond with sulfate ions to form a salt.
- A double replacement reaction occurs because potassium ions bond with sulfate ions to form a salt.
- A single replacement reaction occurs because potassium is more reactive than hydrogen.
- A double replacement reaction occurs because potassium is less reactive than hydrogen.
2. A double replacement reaction occurs because potassium ions bond with sulfate ions to form a salt.
All combustion reactions release energy. (2 points)
True or False
True
Which of the following shows a valid combustion reaction? (4 points)
- 2Al + 2O2 → 2AlO + O2
- C2H4 + 3O2 → 2CO2 + 2H2O
- 2CH4 + O2 → 2CO + 4H2
- Ca + O2 → CaOH
2. C2H4 + 3O2 → 2CO2 + 2H2O
What is true when an element is oxidized? (4 points)
- It bonds with the hydroxide ion.
- It loses electrons to another element.
- It reacts with oxygen gas.
- It takes electrons from another element.
2. It loses electrons to another element.
Which substances in the list can be some of the reactants and products in the same combustion reaction? (4 points)
- 1, 2, and 3
- 2, 3, and 6
- 1, 4, and 5
- 1, 2, and 5

2. 2, 3, and 6
When potassium metal is placed in water, a large amount of energy is released as potassium hydroxide and hydrogen gas are produced in the reaction 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g). Your lab partner says this is a redox reaction and a combustion reaction. Do you agree? Defend your answer by explaining whether or not it meets the requirements of each type of reaction. (6 points)
The reaction is a combustion reaction since there is a reaction with oxygen (the potassium metal interacts with the oxygen in water); furthermore, it releases energy, which is another characteristic of a combustion reaction. However, the lab partner is correct; the reaction is also a redox reaction. In the reactants, the 2K has an oxidation number of 0 since it is a neutral element. However, in the product, potassium in 2KOH has an oxidation number of +2 (+1 * 2), which means an oxidation reaction occurred. Ogyen had a -4 (-2 * 2) oxidation number in the reactants and -4 oxidation number in the product, so it did not change. Hydrogen, which originally had a +4 (+1 * 2 * 2) oxidation number, has a +2 oxidation number in 2KOH. Since hydrogen had an increase in electrons, a reduction occurred, making it the oxidation agent for potassium; however, since potassium had a decrease in electrons, an oxidation reaction occurred, making it the reduction agent.
What is the oxidation number of manganese in MnO41−? (4 points)
- +3
- +4
- +7
- +8
3. +7
What substance is reduced in the reaction 2Fe2+ + Cl2 → 2Fe3+ + 2Cl−? (4 points)
- Cl2, because it gained electrons
- Cl2, because it lost electrons
- Fe2+, because it gained electrons
- Fe2+, because it lost electrons
1. Cl2, because it gained electrons
Why are redox reactions used in batteries? (4 points)
- The attraction between charged ions releases energy.
- The movement of electrons creates an electric current.
- The reactions are extremely exothermic, producing an electric current.
- The reactions are extremely endothermic, inducing the movement of electrons.
- The movement of electrons creates an electric current.
Read the following chemical equation:
2Co + 3F2 → 2CoF3
Which statement best identifies and describes the reducing agent in the reaction? (4 points)
- Co is the reducing agent because its oxidation number increases.
- Co is the reducing agent because its oxidation number decreases.
- F2 is the reducing agent because its oxidation number increases.
- F2 is the reducing agent because its oxidation number decreases.
1. Co is the reducing agent because its oxidation number increases.
In which of the following reactions is chlorine (Cl) oxidized? (4 points)
- Br2 + 2Cl− → Cl2 + 2Br−
- Cl2 + 2e− → 2Cl−
- 2ClO3− + 12H+ → Cl2 + 6H2O
- 2Na + Cl2 → 2NaCl
1. Br2 + 2Cl− → Cl2 + 2Br−
Which of the following reactions could be used to power a battery because of the transfer of electrons? (4 points)
- Pb22+ + 2Br− → PbBr
- CaCl2 + 2NaOH → Ca(OH)2 + 2NaCl
- KOH + HCl → KCl + H2O
- Zn + Cu2+ → Zn2+ + Cu
4. Zn + Cu2+ → Zn2+ + Cu
Why are redox reactions used in batteries? (4 points)
- The attraction between charged ions releases energy.
- The movement of electrons creates an electric current.
- The reactions are extremely exothermic, producing an electric current.
- The reactions are extremely endothermic, inducing the movement of electrons.
2. The movement of electrons creates an electric current.
What are the characteristics of a combustion reaction?
Combustion Reaction: Reaction in which a substance reacts with oxygen gas
- reacts with oxygen
- releases a large amount of energy (light/heat)
- Exothermic
What is an Organic Combustion Reaction?
Compounds contain carbon covalently bonded (and sometimes hydrogen)
CxHx + O2 → H2O + CO2
Hydrocarbon combustion:
- products: carbon and water
Cellular Respiration:
- organic compounds (glucose; C6H12O6) + oxygen = energy
What is an inorganic combustion reaction?
A + O2 → AOx
- burn-in oxygen
- synthesis reactions
- React with oxygen = energy
What are the formulas for organic and inorganic combustion reactions?
CxHx + O2 → H2O + CO2 (organic compounds)
A + O2 → AOx (inorganic compounds)

What is a redox-reaction?
`Oxidation-Reduction (redox) reaction: Reaction electrons exchanged from one substance to another
What is oxidation? What is the reduction?
Oxidation: substance loses one+ electron during reaction → higher, positive oxidation number
- many metals:
react with oxygen → ionic metal oxide compound
Reduction: substance gains one+ electron → lower, negative oxidation number
- decrease charge → decrease reduction
Oxidation and Reduction go together:
- one substance must O if another R
What is the difference between a single replacement or double replacement reaction?
Single Replacement & Redox
- most common
neutral atom → electrostatic charge → new compound
Double Replacement & Redox
- ions do not change charge
What is the oxidation number and what are the 5 rules?
Oxidation Number: a number assigned to an atom of an element that represents the number of electrons lost or gained
- Neutral Elements:
Standard state
Oxidation Number: 0
* O2 * Na * F2 * S8 * P4 2. **_Oxygen_:**
Oxidation Number: -2
except in peroxides: -1
* H20 (O = -2) * CaO (O = -2) * H2O2 = (O = -1) 3. **_Monatomic Ions:_**
Oxidation Number: equal to charge as ion
* NaCl ( Na = +1, Cl = −1) * CaBr2 (Ca = +2, Br = −1) * Ag+ (Ag = +1) * Al3+ ( Al = +3) 4. **_Covalent Compounds:_**
Present compound is ionic with more electronegative element froming anion
Oxidation Number: equal to “charge” of ion
* CCl4 ( C = +4, Cl = −1) * NH3 ( N = −3, H = +1 ) 5. **_All Elements:_**
All oxidation numbers: add up to total charge compound
What are oxidation and reduction?
What is the reduction agent and the oxidation agent?
Oxidation: substance loses one+ electron during reaction → higher, positive oxidation number
- many metals:
react with oxygen → ionic metal oxide compound
Reduction: substance gains one+ electron → lower, negative oxidation number
- decrease charge → decrease reduction
Reduction Agent
Causes another substance to reduce (not reduce itself)
- Reducing agent: reactant is oxidized
Oxidization Agent
Causes another substance to oxidize (not oxidized itself)
- Oxidization Agent: reactant is reduced
What are nuclear reactions?
Nulceus split apart/smaller nuclei are combined
- changes element’s identity
- protons and neutrons gained lost by atoms over the course of the nuclear reaction
“lost” protons become new particles
What is Einstein’s Formula and how does it relate to mass and energy?
E = mc2
Multiplying loss of mass by speed of light squared = amount of energy
Relationship between mass and energy
Regular chemical reaction: Mass and Energy both conserved
Nuclear Reaction:
- mass converted to energy
What is fission?
Elements - greater mass
- often unstable & radioactive
undergo reactions: FISSION
- break apart into smaller atoms
- “missing” mass = energy
Multiplying loss of mass by speed of light squared = amount of energy
What is Fusion?
Occurs Sun
- (theory) replicate on earth
- *
Form one larger element from smaller molecules
- nuclei hurled at each other high speed
- new nucleus: less mass single nuclei
extra mass: energy
Helium = hydrogen + hydrogen
What are the advantages and disadvantages of fission?
Advantages of Fission
- small hydrogen isotopes plentiful
- easy obtain
Disadvantages of Fission
- unstable; not easy control
Define Strong Nuclear forces:
Attractive forces hold the nucleus of an atom together
hold subatomic particles together inside the nucleus
Protons: positive → repel → electromagnetic forces
Strong nuclear forces → override electromagnetic repulsion
- proton stay close in the nucleus
- *
- Strongest four fundamental forces
- Shortest range
Define Weak Nuclear Foces?
What:
- responsible for different types of particle decay
-
Radioactivity
- when nucleus atoms break down
- released charged particles
- Very short range
Define electromagnetism:
Forces that occur when an electromagnetic field interacts with electrically charged particles
Examples:
- electricity
- magnetism
- static
- light
- electromagnetic spectrum
- molecular bonds
- Second strongest
- Only force both attract and repel (depending on charge)
- Very long range
Define Gravity:
an attraction force that pulls two objects together
weaker the farther objects are apart
weight: a combination of mass and gravitational force
* * *
- Weakest
- longest range
Define Radioactive decay:
nuclei break down to form a different substance and release radiation in process.
What is Alpha decay?
Alpha (α)
The steam of alpha particles
- 2 protons & two neutrons
- positive charge
Atom releases alpha particle:
- atomic number decrease -2
- Mass number decrease -4
Properties:
- high kinetic energy
- cause damage surface (skin and living tissue)
-
easy shield against
- not penetrate paper
- move through air → neutral helium atoms
Define Beta Decay?
Beta (β)
Steam beta particles
- fast-moving electrons released from the nucleus when neutrons break apart into:
- 1 proton
- 1 election
Negative beta particle:
- one more proton and one less neutron
Properties:
- negative charge
- faster than alpha
- more difficult protect against
- penetrate cloth and paper
- kill cells
- not penetrate aliminum
What is Gamma decay?
Gamma (γ)
Gamma Radiation: given off during different types of nuclear decay
- electromagnetic waves
- high frequency
- greater energy than ultraviolent/x-rays
Properties:
- high energy
- no mass or charge
- penetrate through most materials
- damange
- not penetrate lead
Define transmutation:
the changes of identity of an element due to radioactive decay
What are Uranium (Alpha Decay) Transmutations?
Uranium [Alpha Decay]
Radioactive uranium-238:
goes through alpha decay → alpha particle
- 2 protons
- 2 neutrons
- leave thorium-234
During reaction: energy released (kinetic)
- atomic number decrease -2
- mass number decrease -4
What is Thorium (Beta) Decay?
Thorium [Beta Decay]
Thorium-234:
beta particle
- atomic number increases +1
- mass number same
Define the rate of Radioactive Decay:
Measure: HALF-LIFE
- the time it takes for the radioactivity level of an isotope
- decrease to half its original value
Property:
- isotope is constant
- independent of external conditions
Radium-226 → half-life 1,620 years
half given sample decay half end 1,620 years