CHEMICAL EQUATIONS AND REACTIONS

What do chemical equations represent?

The reactants and products involved in a chemical reaction.

What is the law of conservation of mass?

Matter cannot be created or destroyed.

Why is balancing chemical equations essential?

To ensure the number of atoms for each element is equal on both sides of the equation.

What are some observable signs that a chemical reaction has occurred?

Change in color, change in state, evolution of gas, and change in temperature.

What is a cation?

A positively charged ion.

Give an example of a cation with a valency of +1.

Sodium ($Na^{+1}$).

What is the valency of Magnesium?

+2.

What do positive ions with a valency of +3 include?

Aluminium ($Al^{3+}$) and Iron (III) or Ferric ($Fe^{3+}$).

What is an anion?

A negatively charged ion.

Give an example of an anion with a valency of -2.

Carbonate ($CO_3^{2-}$).

How is sodium chloride formed from its ions?

Sodium ($Na^{+1}$) and Chloride ($Cl^{-1}$) cancel out to form $NaCl$.

What is the definition of balancing chemical equations?

Ensuring the number of atoms of each element is equal on both the reactant and product sides of the equation.

What does the law of conservation of mass state?

Mass can neither be created nor destroyed in a chemical reaction.

What is the first step in the hierarchical balancing method?

Balance metals first.

What denotes an exothermic reaction?

A reaction that releases heat.

What indicates a change in state in a chemical reaction?

The substance changes from solid to liquid, liquid to gas, etc.

What is a combination reaction?

A reaction where two or more reactants combine to form a single product ($A + B ightarrow C$).

Provide an example of a combination reaction.

The burning of magnesium ribbon: $2Mg(s) + O_2(g) ightarrow 2MgO(s) + Heat$.

What happens when quick lime reacts with water?

It forms slaked lime ($Ca(OH)_2$) and releases heat.

What type of reaction occurs when slaked lime reacts with carbon dioxide?

A precipitation reaction and formation of calcium carbonate.

What is decomposition reaction?

A reaction where a single reactant breaks down into two or more simpler products.

What is thermal decomposition?

Decomposition that occurs through the application of heat.

What happens to iron (II) sulfate when heated?

It decomposes into iron (III) oxide, sulfur dioxide, and sulfur trioxide.

What is electrolytic decomposition?

Decomposition that occurs using electrical energy.

What is the electrolysis of water represented as?

$2H_2O(l) ightarrow 2H_2(g) + O_2(g)$.

What is photochemical decomposition?

Decomposition that occurs using light energy.

Give an example of photochemical decomposition.

The decomposition of silver chloride: $2AgCl(s) ightarrow 2Ag(s) + Cl_2(g)$.

What is a displacement reaction?

A reaction where a more reactive element displaces a less reactive element from its compound.

What is the reactivity series?

A list of metals arranged in order of decreasing reactivity.

What happens when iron is placed in copper sulfate?

Iron displaces copper, changing the blue copper sulfate to light green ferrous sulfate.

What type of reaction is double displacement?

A reaction where there is an exchange of ions between reactants to form new compounds.

What is a precipitation reaction?

A specific double displacement reaction resulting in an insoluble solid.

Give an example of a precipitation reaction.

The reaction of sodium sulfate and barium chloride to form barium sulfate.

What is oxidation in a chemical reaction?

Gain of oxygen or loss of hydrogen.

What is reduction in a chemical reaction?

Loss of oxygen or gain of hydrogen.

What is a redox reaction?

A reaction where oxidation and reduction occur simultaneously.

What does corrosion refer to?

The slow eating away of metal surfaces by air, moisture, or chemicals.

What is rancidity in food?

The oxidation of fats and oils in food, leading to unpleasant odor and taste.

What differentiates a chemical change from a physical change?

A chemical change results in new substances, while a physical change does not.

Why do we clean magnesium ribbon with sandpaper before burning it?

To remove the protective layer of magnesium oxide that prevents effective burning.

What should be done to prevent the unintentional decomposition of light-sensitive chemicals?

Store them in dark or black bottles.

What color change indicates that copper has been displaced by iron?

The blue color of copper sulfate fades to light green ferrous sulfate.

Why is the amount of hydrogen gas collected in electrolysis double that of oxygen?

Because there are two parts of hydrogen for every one part of oxygen in water ($H_2O$).

What does the acronym FACTS stand for in identifying chemical reactions?

Formation of Precipitate, Altered Color, Concentration/Evolution of Gas, Temperature Change, State Change.

What happens to calcium carbonate when slaked lime reacts with carbon dioxide?

Calcium carbonate precipitates out over 2-3 days.

What is needed to ensure the electrolysis of water is effective?

A few drops of acid like $H_2SO_4$ to improve conductivity.

What is the reaction of copper oxidation with oxygen?

$2Cu + O_2 ightarrow 2CuO$.

What happens during the oxidation of fats and oils?

It results in rancidity, which affects the smell and taste of food.

What distinguishes an endothermic reaction?

It requires the absorption of energy to proceed.

What compound is formed when magnesium burns in oxygen?

Magnesium oxide ($MgO$).

What is the product of the thermal decomposition of lead nitrate?

Lead oxide, nitrogen dioxide, and oxygen.

What does the law of conservation of mass require during a reaction?

That the total mass of reactants equals the total mass of products.

What reflects the characteristic sound made when lead nitrate decomposes?

A characteristic cracking sound.

How do you identify an endothermic reaction?

It absorbs energy from the surroundings.

What ions remain in solution after a precipitation reaction between sodium sulfate and barium chloride?

Sodium ($Na^{+}$) and Chloride ($Cl^{-}$) ions.

What occurs when copper oxidizes with heat?

Copper transitions from reddish-brown to black copper oxide.

What can be used to combat rancidity in food?

Adding antioxidants and storing food in airtight containers.

What can indicate a gas has evolved in a chemical reaction?

Bubbles or fumes observed during the reaction.

What type of reaction is the electrolysis of water?

A decomposition reaction using electrical energy.

What type of reaction occurs with burning magnesium?

A combination reaction that also releases heat.

What results from the electrolysis of water in terms of gases?

Collection of hydrogen gas at the cathode and oxygen gas at the anode.

What are brown gases observed during lead nitrate decomposition?

Nitrogen dioxide ($NO_2$).

What is meant by a combustion reaction?

A type of reaction involving the burning of a substance in the presence of oxygen.

What properties define a physical change?

No new substances are formed; changes in state, shape, or size occur.

What can be inferred from the loss of mass during a reaction?

It may indicate the production of gas that escaped into the environment.

What do we observe when iron reacts with copper sulfate?

The solution turns from blue to light green as iron displaces copper.

What is formed when calcium oxide reacts vigorously with water?

Calcium hydroxide, known as slaked lime.

What does adding to pure water to improve electrical conductivity during electrolysis?

Adding a few drops of acid.

What would happen if magnesium oxide is not removed from the magnesium ribbon before burning?

The ribbon would not burn effectively due to the protective layer.

What is the visual indication during magnesium burning?

It emits a dazzling white flame.

How many moles of hydrogen are produced from one mole of water during electrolysis?

Two moles of hydrogen.

What represents a typical redox reaction?

A reaction where both oxidation and reduction occur simultaneously.

How do we write the balanced reaction for iron and copper sulfate?

$Fe(s) + CuSO_4(aq) ightarrow FeSO_4(aq) + Cu(s)$.

In the reaction $MnO_2 + 4HCl \rightarrow MnCl_2 + 2H_2O + Cl_2$, what is oxidized?

$HCl$ is oxidized to $Cl_2$.

In a redox reaction, what is the function of the oxidizing agent?

It undergoes reduction and accepts electrons.

In a redox reaction, what is the function of the reducing agent?

It undergoes oxidation and donates electrons.

What will likely happen if you expose slaked lime to atmospheric carbon dioxide?

It will react slowly and form calcium carbonate.

What do you call the color change in lead nitrate upon heating?

Colorless lead nitrate turns yellow when decomposed.

Which ions react to form a yellow precipitate when lead nitrate and potassium iodide mix?

Lead ions ($Pb^{2+}$) and iodide ions ($I^{-}$).

What happens when hydrogen gas burns in oxygen?

It forms water ($H_2O$) and releases energy.

What do you call it when a precipitate forms in a double displacement reaction?

A precipitation reaction.

What happens to aluminum in an electrolysis reaction with oxygen?

It gets oxidized by gaining oxygen.

What chemical change occurs when fats oxidize in food?

It results in rancidity, leading to off-flavors.