Chemical Changes Flashcards
What is the pH scale range for acidic solutions?
The pH scale indicates that acidic solutions have a pH range of 0 to 6.
What pH value is considered neutral?
A pH value of 7 is considered neutral, indicating neither acidity nor alkalinity.
What are common examples of bases?
Common bases include sodium hydroxide and calcium carbonate.
What is the pH range for alkaline (basic) solutions?
Alkaline solutions have a pH range from 8 to 14.
What defines an acid in terms of pH and ion release?
An acid is defined as a substance that forms aqueous solutions with a pH less than 7 and releases hydrogen ions (H+) in water.
What is the definition of an alkali?
An alkali is a subgroup of bases that are soluble in water and form hydroxide ions (OH-) resulting in a pH greater than 7.
What defines a base in terms of pH?
A base is defined as any substance with a pH greater than 7.
What is the result of the neutralization reaction between hydrochloric acid and sodium hydroxide?
The reaction produces sodium chloride (salt) and water.
What is a neutralization reaction?
A neutralization reaction occurs when an acid and a base react to produce a salt and water.
What do universal indicators do?
Universal indicators are chemical dyes that change color across a wide pH range, indicating the acidity or alkalinity of a solution.
Why are pH probes preferred over indicators for measuring pH?
pH probes provide more accurate and precise measurements by eliminating human judgment in color interpretation.
What are common examples of acids?
Common acids include hydrochloric acid, sulfuric acid, and nitric acid.
What ions are involved in the neutralization reaction of acids and bases?
Hydrogen ions (H+) from the acid and hydroxide ions (OH-) from the base combine to form water (H2O).
What is the role of hydroxide ions in alkaline solutions?
Hydroxide ions (OH-) are produced by alkalis in solution, contributing to a pH greater than 7.
What happens to pH during a neutralization reaction?
The pH of the resulting solution from a neutralization reaction typically becomes neutral at pH 7.
Definition of Strong Acids
Strong acids are acids that completely dissociate into ions in solution.
What is the common characteristic of alkalis?
Alkalis are characterized by their solubility in water and their ability to produce hydroxide ions.
Definition of Weak Acids
Weak acids are acids that only partially dissociate into ions in solution, establishing an equilibrium between the dissociated ions and the undissociated acid.
Examples of Weak Acids
Ethanoic acid (CH3COOH), Citric acid, and Carbonic acid (H2CO3) are examples of weak acids
Acidic Solution Requirements
To achieve a low pH, a high concentration of hydrogen ions is needed.
Examples of Strong Acids
Hydrochloric acid (HCl), Nitric acid (HNO3), and Sulfuric acid (H2SO4) are examples of strong acids.
General Rule for Strong vs Weak Acids
At any given concentration, a strong acid will have a lower pH than a weak acid due to a higher proportion of dissociated molecules.
What is the relationship between acid strength and concentration?
Acid strength refers to the degree of ionization of acid molecules, while concentration measures the amount of acid present in a certain volume.
Why do weak acids require higher concentrations to achieve low pH?
Weak acids require higher concentrations to achieve low pH because only a small fraction of their molecules ionize.
What defines a strong acid?
A strong acid is defined as an acid that ionizes completely in aqueous solutions, releasing hydrogen ions.
What is the relationship between strong acids and pH at various concentrations?
Strong acids can achieve low pH at most concentrations due to complete dissociation.
How does pH relate to hydrogen ion concentration?
pH is inversely related to hydrogen ion concentration; as [H+] increases, pH decreases.
What characterizes weak acids?
Weak acids do not fully ionize in aqueous solutions; only a small portion of acid particles dissociate to release hydrogen ions.
What is the general reaction between acids and metal oxides or hydroxides?
Acid + Metal Oxide/Hydroxide → Salt + Water.
What is the key process in the reaction of acids with bases?
The negative ion from the acid combines with the positive ion from the base to form a salt, and water is always produced.
What is produced when hydrochloric acid reacts with sodium oxide?
The reaction produces sodium chloride (NaCl) and water (H2O).
What is the general reaction when acids interact with metal carbonates?
Acid + Metal Carbonate → Salt + Water + Carbon Dioxide.
What are the steps to prepare a soluble salt from an insoluble base?
- Heat dilute acid, 2. Add insoluble base, 3. Neutralize, 4. Filter excess base, 5. Evaporate water, 6. Crystallize, 7. Collect crystals, 8. Dry crystals.
How do you determine when the acid has been fully neutralized during the salt preparation?
The base will stop disappearing, indicating it is in excess and all the acid has been neutralized.
What is the general trend in the violence of metal reactions with acids?
The reactions become less violent as you move down the reactivity series from potassium to magnesium, zinc, iron, and copper.
What is the role of heating in the preparation of soluble salts?
Heating the filtered solution helps to evaporate water, allowing salt crystals to form.
What is the importance of using a water bath instead of a Bunsen burner during evaporation?
A water bath prevents overheating, which could damage the salt.
What happens to the solution as it cools after heating during crystallization?
More salt crystals will form as the solution cools.
What is the final step in drying the crystals obtained from the soluble salt preparation?
The crystals can be dried by dabbing with filter paper or leaving them in a warm place.
Which metals can react with water?
Only the most reactive metals, like lithium, can react with water; zinc, iron, and copper do not react.
What happens when metals react with water?
When metals react with water, they form metal hydroxides and hydrogen gas.
How do metals react with acids?
When a metal reacts with an acid, it produces a salt and hydrogen gas.
What happens in the displacement reaction between magnesium and iron sulfate?
Magnesium displaces iron in iron sulfate to form magnesium sulfate and iron.
What is the reactivity series?
The reactivity series is a ranking of metals based on their reactivity, with group 1 metals being the most reactive and transition metals generally the least.
Why does copper not displace iron in iron sulfate?
Copper cannot displace iron because it is less reactive than iron.
What is a displacement reaction?
A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its compound.
What is produced when lithium reacts with water?
Lithium reacts with water to form lithium hydroxide and hydrogen gas.
What factors are important for fair testing when comparing metal reactivity?
Fair testing requires using the same mass and surface area of metal samples and the same type and concentration of acid.
What is the general reaction for reducing metal oxides with carbon?
The reaction is: Metal Oxide + Carbon -> Pure Metal + Carbon Dioxide.
What happens to the metal during the reduction process with carbon?
The metal is reduced because it loses oxygen.
What is oxidation in terms of oxygen?
Oxidation is the process of gaining oxygen.
What is the relationship between oxidation and reduction in chemical reactions?
Oxidation and reduction are complementary processes where one substance gains oxygen (oxidized) and another loses oxygen (reduced)
How do metals typically react with oxygen?
Most metals oxidize into metal oxides when exposed to oxygen.
What are redox reactions?
Redox reactions are chemical reactions in which oxidation and reduction occur simultaneously.
What is the alternative method for extracting more reactive metals?
More reactive metals require electrolysis for extraction, which is an expensive process.
What is oxidation in terms of electrons?
Oxidation is defined as the loss of electrons from an atom or ion.
What is a half equation?
A half equation shows the gain or loss of electrons for a specific element involved in a redox reaction.
Which metals are often found as pure metals due to their lack of reactivity?
Unreactive metals like gold are often found as pure metals because they do not react with oxygen.
What is reduction in terms of electrons?
Reduction is defined as the gain of electrons by an atom or ion.
What is the role of spectator ions in ionic equations?
Spectator ions are ions that do not change during a reaction and are removed from ionic equations.
What is the overall charge balance check in half equations?
The overall charge on each side of a half equation must be equal to ensure electrons are correctly placed.
How does the reactivity series relate to displacement reactions?
The reactivity series ranks metals by their reactivity, determining which metal can displace another in a reaction.
How is an ionic equation simplified?
An ionic equation is simplified by including only the ions that participate in the reaction.
What does the reactivity series indicate?
The reactivity series ranks metals by their reactivity, determining which metals can displace others in reactions.
What is the reduction half equation for iron?
The reduction half equation for iron is Fe²⁺ + 2e⁻ → Fe.
Why are sulfate ions considered spectator ions in the calcium and iron sulfate reaction?
Sulfate ions are spectator ions because they do not participate in the electron transfer and remain unchanged.
What is the definition of a redox reaction in terms of electron transfer?
A redox reaction involves the transfer of electrons where one substance is oxidized and another is reduced.
What does it mean for a substance to be oxidized?
A substance is oxidized when it loses electrons, resulting in an increase in its oxidation state.
What is the significance of identifying half equations in redox reactions?
Identifying half equations helps clarify the specific electron transfer processes for each substance involved.
How do you determine if electrons are on the correct side of a half equation
You determine the correct side for electrons by ensuring that the overall charge balances on both sides of the equation
What does it mean for a substance to be reduced?
A substance is reduced when it gains electrons, resulting in a decrease in its oxidation state.
How are ionic equations useful in chemistry?
Ionic equations are useful as they clarify the specific ions that participate in a chemical reaction.
What is the significance of balancing half equations?
Balancing half equations is crucial for accurately representing the electron transfer and ensuring charge conservation.
What happens to the overall charge in a balanced half equation?
In a balanced half equation, the total charge on both sides must be equal to confirm the reaction’s correctness.
How can you identify which metal will displace another in a reaction?
You can identify the more reactive metal using the reactivity series to predict displacement in a reaction
What defines a more reactive metal in a displacement reaction?
A more reactive metal is defined as one that can displace a less reactive metal from its compound.
Why are ionic equations useful in chemistry?
Ionic equations are useful because they simplify reactions by highlighting the species that undergo change, improving understanding.
What is electrolysis?
Electrolysis is a process that uses electricity to split up a substance, specifically to separate elements in insoluble ionic compounds.
What is an electrolyte?
An electrolyte is a liquid or solution containing an ionic compound where the ions are free to move.
What is the function of the anode in electrolysis?
The anode is the positive electrode where oxidation occurs, attracting negative ions.
How do you prepare an electrolyte from an insoluble ionic compound?
To prepare an electrolyte from an insoluble ionic compound like lead bromide, it must be melted to create a molten liquid.
What are the components of electrolysis equipment?
The key components include a beaker, electrolyte, electrodes, wires, and a power supply (battery).
What is the function of the cathode in electrolysis?
The cathode is the negative electrode where reduction occurs, attracting positive ions.
What is the overall process of electron transfer in electrolysis?
Electrons from bromide ions are transferred to the anode, travel through the wire to the cathode, and are given to lead ions to form pure lead.
What is meant by ‘discharge’ in the context of electrolysis?
Discharge refers to the process where a charged ion becomes a neutral atom.
What is the role of the power supply in electrolysis?
The power supply (battery) drives the flow of electrons between the electrodes.
What is the outcome of electrolysis using molten lead bromide?
Electrolysis of molten lead bromide results in the separation of lead and bromine into their pure elemental forms.
What are the electrodes used in the electrolysis of molten aluminum oxide?
Two carbon electrodes are used: the anode (positive) and the cathode (negative).
How does the state of the electrolyte differ between soluble and insoluble ionic compounds?
Soluble ionic compounds form aqueous solutions, while insoluble ionic compounds must be melted to become molten liquids.
What is the significance of oxidation and reduction in electrolysis?
Oxidation and reduction are critical processes that occur at the electrodes, enabling the conversion of ions to their elemental forms.
Why must the ions in an electrolyte be free to move?
Ions must be free to move in order to conduct electricity and facilitate the electrochemical reactions during electrolysis.
What is the relationship between oxidation and reduction at the electrodes?
Oxidation occurs at the anode (loss of electrons) while reduction occurs at the cathode (gain of electrons).
What is the relationship between electrolysis and ionic compounds?
Electrolysis is specifically used to separate and extract elements from ionic compounds, particularly when they are insoluble.
What is the significance of oxidation and reduction in electrolysis?
Oxidation occurs at the anode as ions lose electrons, while reduction occurs at the cathode as ions gain electrons.
What is the significance of the melting point of aluminum oxide in electrolysis?
Aluminum oxide has a high melting point (over 2000°C), necessitating energy-intensive processes to melt it.
What must happen to aluminum oxide before it can be used in electrolysis?
Aluminum oxide must be purified and melted to become a liquid electrolyte for electrolysis.
Why is it necessary to melt aluminum oxide before electrolysis?
Melting aluminum oxide allows the ions to move freely, which is required for electrolysis to occur.
What is the first step in the electrolysis process for aluminum extraction?
The first step is to purify aluminum oxide from bauxite.
What is the purpose of the power source in the electrolysis setup?
The power source provides the necessary electric current to facilitate the electrolysis reaction.
What occurs at the cathode during the electrolysis process?
Aluminum 3+ ions gain electrons from the cathode and are reduced to form molten aluminum.
How is aluminum oxide obtained from bauxite?
Aluminum oxide is purified from bauxite before it can be used in electrolysis.
What are the products of the electrolysis of aluminum oxide?
The products are pure aluminum (liquid) and oxygen gas.
What role does cryolite play in the electrolysis of aluminum?
Cryolite is mixed with aluminum oxide to lower its melting point for easier electrolysis.
What is the purpose of electrolysis in metal extraction?
Electrolysis is used to separate ionic compounds into their pure elements by passing electric current through an electrolyte.
How is the aluminum collected after electrolysis?
Molten aluminum metal accumulates at the bottom of the beaker during the electrolysis process.
For which metals is carbon reduction effective?
Carbon reduction is effective for metals less reactive than carbon, such as zinc, iron, and copper.
What is the main challenge when using electrolysis for aluminum oxide?
Aluminum oxide is solid, preventing ion mobility necessary for electrolysis.
