2B3 Basic Principles of Chemical Reactions Flashcards
Explain how chemical reactions depend on factors affecting reaction rate and equilibrium.
What is a chemical reaction?
A process where reactants are transformed into new substances called products.
Chemical reactions involve the breaking and forming of chemical bonds.
Examples include combustion, synthesis, and decomposition reactions.
What is a chemical equation?
A representation of a chemical reaction using symbols and formulas.
Chemical equations show the reactants, products, and their relationships in terms of atomic and molecular formulas.
Define:
Reactant
A substance that undergoes transformation in a chemical reaction to form products.
Reactants are the starting materials in a chemical reaction that undergo change to form products.
What is a product in a chemical reaction?
A substance that is formed as a result of a chemical reaction.
Products are the new substances produced after reactants undergo chemical change during a reaction.
Fill in the blank:
In a chemical equation, the reactants are on the _____ side, and the products are on the _____ side.
left, right
Reactants are substances that undergo chemical changes, while products are the new substances formed after the reaction.
What does the symbol “→” in a chemical equation represent?
Produces or yields
This arrow separates the reactants (on the left) from the products (on the right) in a chemical reaction.
True or False:
In a chemical equation, the number of atoms of each element is conserved.
True
The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction, so the number of atoms of each element must remain the same before and after the reaction.
What is the general format for writing a chemical equation?
Reactants → Products
Reactants are written on the left side of the equation, and products are written on the right side, separated by an arrow indicating the direction of the reaction.
True or False:
The number of atoms of an element can change when balancing a chemical equation.
False
Balancing an equation involves adjusting coefficients, not changing subscripts in chemical formulas, to ensure the same number of atoms on both sides.
How is a chemical equation balanced?
By adjusting the coefficients to equalize the number of atoms on both sides.
Coefficients are whole numbers used to balance the equation, ensuring the law of conservation of mass is followed.
What is a coefficient in a chemical equation?
A number placed in front of a chemical formula to balance the equation.
Coefficients show the relative amounts of reactants and products involved in the reaction.
What does the coefficient in a balanced equation represent?
The number of molecules or moles of a substance.
Coefficients indicate the relative amounts of reactants and products involved in the reaction, helping to balance the equation.
Fill in the blank:
In balancing equations, coefficients must be written as _______ numbers.
whole
Coefficients must be integers (whole numbers) to maintain the proper ratio between reactants and products.
In the equation 2H₂ + O₂ → 2H₂O, what is the coefficient of water (H₂O)?
2
The coefficient of 2 in front of H₂O indicates that two molecules of water are produced from the reaction of hydrogen and oxygen.
True or False:
Balancing chemical equations involves changing the subscripts in chemical formulas.
False
Subscripts in chemical formulas represent the fixed number of atoms in a molecule and cannot be changed; only coefficients can be adjusted when balancing equations.
Fill in the blank:
In a balanced chemical equation, the total mass of the _______ equals the total mass of the ________.
reactants, products
This reflects the principle of the conservation of mass, which states that mass is neither created nor destroyed during a chemical reaction.
Define:
Stoichiometry
The calculation of the quantities of reactants and products in a chemical reaction.
Stoichiometry uses the relationships from a balanced equation to calculate amounts of substances involved in reactions.
True or False:
Balancing chemical equations is necessary for performing stoichiometric calculations.
True
Balanced equations provide the correct proportions of reactants and products, which are crucial for determining quantities in mass-mole calculations.
What is a combustion reaction?
A reaction with oxygen that produces heat, light, carbon dioxide, and water.
An example is the burning of methane: CH₄ + 2O₂ → CO₂ + 2H₂O.
Fill in the blank:
A combustion reaction always involves a/an _______ and oxygen.
fuel
Fuels such as hydrocarbons, alcohols, or organic compounds undergo combustion with oxygen to release energy.
What is a neutralization reaction?
A reaction between an acid and a base to produce water and a salt.
For example, HCl + NaOH → NaCl + H₂O, where hydrochloric acid neutralizes sodium hydroxide.
What is a synthesis reaction?
Two or more substances combine to form a more complex product.
An example is 2H₂ + O₂ → 2H₂O, where hydrogen and oxygen combine to form water.
True or False:
In a neutralization reaction, the products formed are water and a salt.
True
In neutralization, the hydrogen ions (H⁺) from the acid combine with hydroxide ions (OH⁻) from the base to form water.
Fill in the blank:
A synthesis reaction is also called a ________ reaction.
combination
This is because two or more reactants combine to create a single product.
What is a decomposition reaction?
A reaction where a compound breaks down into two or more simpler substances.
For example, 2H₂O₂ → 2H₂O + O₂, where hydrogen peroxide decomposes into water and oxygen.
True or False:
In a decomposition reaction, energy is often required to break bonds in the reactant.
True
Decomposition reactions often require heat, light, or electricity to break the bonds of the reactant.
What is a single replacement reaction?
A reaction where one element replaces another element in a compound.
An example is Zn + 2HCl → ZnCl₂ + H₂, where zinc replaces hydrogen in hydrochloric acid.
What is a double replacement reaction?
Two compounds exchange ions or elements to form two new compounds.
An example is AgNO₃ + NaCl → AgCl + NaNO₃, where silver nitrate reacts with sodium chloride to form silver chloride and sodium nitrate.
What type of reaction is represented by the equation, Fe + CuSO₄ → FeSO₄ + Cu?
Single replacement reaction
In this reaction, iron (Fe) replaces copper (Cu) in copper sulfate (CuSO₄), forming iron sulfate (FeSO₄) and copper.
What is an oxidation-reduction (redox) reaction?
A reaction where electrons are transferred, causing oxidation and reduction.
Oxidation involves the loss of electrons, while reduction involves the gain of electrons.
What is a precipitation reaction?
A reaction where two aqueous solutions form an insoluble solid (precipitate).
Precipitation reactions often occur when ions in solution combine to form a compound that is not soluble in water.
Fill in the blank:
In a double replacement reaction, the two compounds ________ ions to form new compounds.
exchange
This type of reaction often produces a precipitate, gas, or water as a product.
In an oxidation-reduction reaction, what happens to the substance that undergoes oxidation?
It loses electrons.
For example, in the reaction 2Na + Cl₂ → 2NaCl, sodium (Na) loses electrons, becoming oxidized.
What happens to the substance that undergoes reduction in a redox reaction?
It gains electrons.
Reduction refers to the gain of electrons, which decreases the oxidation state of the substance involved.
What is the term used for the substance that gains electrons in a redox reaction?
The oxidizing agent.
The oxidizing agent causes the oxidation of another substance by accepting electrons.
What is the term used for the substance that loses electrons in a redox reaction?
The reducing agent.
The reducing agent causes the reduction of another substance by donating electrons.
Fill in the blanks:
In the reaction 2Na + Cl₂ → 2NaCl, sodium is ________ and chlorine is ________.
oxidized, reduced
Sodium loses electrons (oxidation), while chlorine gains electrons (reduction) in the reaction.
What is the general equation for combustion?
Fuel + O₂ → CO₂ + H₂O + energy
This equation represents the combustion of hydrocarbons, such as methane, that produce carbon dioxide, water, and energy when they react with oxygen.
What is the first step in a mass-to-mole calculation?
Convert the mass of the substance to moles using its molar mass.
Use the formula: moles = mass (g) / molar mass (g/mol) to convert mass into moles before using stoichiometry.
In the reaction N₂ + 3H₂ → 2NH₃, how many moles of nitrogen (N₂) are needed to react with 9 moles of hydrogen (H₂)?
3
According to the mole ratio, 1 mole of nitrogen reacts with 3 moles of hydrogen, so 9 moles of hydrogen would require 3 moles of nitrogen.
True or False:
The law of conservation of mass is used in mass-mole calculations.
True
Mass-mole calculations are based on the principle that mass is conserved in chemical reactions, meaning the mass of reactants equals the mass of products.
If 32 grams of oxygen gas (O₂) react, how many moles of O₂ are involved?
1
The molar mass of O₂ is 32 g/mol, so 32 grams of O₂ is exactly 1 mole of O₂.
What is a mole-to-mole ratio?
The ratio of moles of one substance to another in a balanced equation.
It’s based on the coefficients of the balanced equation. For example, in: 2H₂ + O₂ → 2H₂O,
- The ratio of H₂ to H₂O is 1:1.
- The ratio of O₂ to H₂O is 1:2.
In the reaction N₂ + 3H₂ → 2NH₃, how many moles of NH₃ will be produced from 6 moles of H₂?
4
The balanced equation shows a 3:2 mole ratio between H₂ and NH₃, so 6 moles of H₂ will produce 4 moles of NH₃.
What is the mole-to-mole ratio in the reaction 2H₂ + O₂ → 2H₂O?
2:1:2 (H₂:O₂:H₂O)
The coefficients of the balanced equation give the mole ratio, meaning for every 2 moles of H₂, 1 mole of O₂ reacts to produce 2 moles of H₂O.
In the equation 2H₂ + O₂ → 2H₂O, what is the ratio of hydrogen (H₂) to oxygen (O₂)?
2:1
The coefficients show that two molecules of hydrogen react with one molecule of oxygen to form water.
What is the reaction rate?
The speed at which reactants are converted into products.
It can be measured by the change in concentration of reactants or products per unit time.
Which factors can affect the rate of a chemical reaction?
- Concentration
- Surface area
- Temperature
- Pressure
- Activation energy
- Catalysts
These factors influence how often and how energetically particles collide.
True or False:
Increasing the concentration of reactants increases the reaction rate.
True
A higher concentration leads to more frequent collisions between reactant particles.
Fill in the blank:
Increasing the ______ ____ of a reactant increases the reaction rate by exposing more particles to collisions.
surface area
For example, powdered solids react faster than solid blocks because of their larger surface area.
What is activation energy?
The minimum energy needed for a reaction to occur.
If reactant particles don’t have enough energy to overcome this barrier, no reaction will happen.
How does temperature affect reaction rate?
Higher temperature increases reaction rate.
Heat provides particles with more energy, making collisions more frequent and effective.
True or False:
A catalyst is consumed during a reaction.
False
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.
Fill in the blank:
Catalysts work by providing a/an _______ reaction pathway with lower activation energy.
alternative
This pathway increases the number of effective collisions.
How does pressure affect the reaction rate in gases?
Increasing pressure increases reaction rate.
Higher pressure forces particles closer together, leading to more frequent collisions.
What is chemical equilibrium?
A state where the forward and reverse reaction rates are equal.
At equilibrium, the concentrations of reactants and products remain constant over time.
Fill in the blank:
Le Chatelier’s Principle states that a system at equilibrium will adjust to _______ a disturbance.
counteract
The system shifts to reduce the impact of changes in concentration, temperature, or pressure.
What happens when more reactants are added to a system at equilibrium?
It shifts toward the products.
Increasing reactant concentration drives the reaction forward to balance the system.
What happens to equilibrium in an exothermic reaction if the temperature is increased?
It shifts toward the reactants.
Heat acts as a product in exothermic reactions, so adding heat pushes the equilibrium backward.
Fill in the blank:
In a system involving gases, increasing the pressure shifts equilibrium toward the side with _______ gas molecules.
fewer
Higher pressure reduces the volume, so the system adjusts by favoring the side with fewer molecules.
True or False:
Catalysts change the position of equilibrium.
False
Catalysts speed up the attainment of equilibrium but do not alter the equilibrium position.
What happens to equilibrium if the concentration of a product is increased?
It shifts toward the reactants.
The system reduces the product concentration by favoring the reverse reaction.
What is the effect of adding an inert gas at constant volume on the equilibrium position?
It has no effect.
Inert gases do not participate in the reaction or alter the concentrations of reactants or products.
In the reaction N₂ + 3H₂ ⇌ 2NH₃, what happens if the concentration of ammonia (NH₃) is increased?
The equilibrium shifts toward the reactants.
According to Le Chatelier’s Principle, increasing the concentration of products drives the reaction toward the reactants to balance the system.
What is the common ion effect?
The shift in equilibrium caused by adding an ion already present in the system.
For example, adding NaCl to a solution of AgCl decreases AgCl’s solubility by increasing the concentration of Cl⁻ ions.
True or False:
Catalysts are widely used in industrial processes to increase reaction rates.
True
Catalysts like platinum in catalytic converters speed up reactions and save energy.
Why does refrigeration slow down food spoilage?
Lower temperature decreases reaction rates.
Cold temperatures reduce the energy of particles, making enzymatic and microbial reactions slower.
What role do catalysts play in industrial processes like combustion?
It can optimize processes.
In combustion, catalysts do not directly affect the combustion reaction itself but can help reduce harmful emissions and make the process more efficient.
True or False:
Enzymes are biological catalysts that speed up reactions in the body.
True
Enzymes lower activation energy, enabling faster biological processes like digestion.
What happens to equilibrium in carbonated drinks when the bottle is opened?
Equilibrium shifts to release more CO₂ gas.
In carbonated drinks, the dissolved CO₂ gas (carbon dioxide) is in equilibrium with the gas above the liquid. Lower pressure upon opening the bottle causes the system to shift, releasing CO₂ gas, which forms bubbles and creates the characteristic fizz.
