Chemistry Reflection 12

Today, in Chemistry, I learn that oxidation is addition of oxygen and that reduction is removal of oxygen. An example is ...

Lead Oxide + Carbon = Lead + Carbon Monoxide

The lead oxide is reduced to lead because oxygen is removed. The carbon is oxidised to carbon monoxide because oxygen is added. 

It can also be that oxidisation is losing electrons while reduction is gaining electrons. We also review and learn about half-equations. We also do group work where we focus one on a solution. The solution I did is Fe(NO₃)₃ solution where we draw the lab setup.

The ions that are present in the solution is Nitrate, Iron, Hydrogen and Hydroxide.

In the negative electrode which is the cathode, the hydrogen escape as gas while the Iron stays inside the solution.

In the positive electrode which is the anode, the hydroxide escape as gas while the Nitrate stays inside the solution.

The half equation is...

Fe³⁺ + 3e^- = Fe_(s)

NO^3- = e^- +NO₃

Chemistry Reflection 11

Today in Chemistry, I learn about Electrolysis. Electrolysis is when ionic substances is broken down by using electricity.

 Ionic substances form when a metal reacts with a non-metal. They contain charged particles called ions. For example, sodium chloride forms when sodium reacts with chlorine. It contains positively charged sodium ions and negatively charged chloride ions. In electrolysis, the ions are free to move because it is dissolved in water. For example, if electricity is passed through copper chloride solution, the copper chloride is broken down to form copper metal and chlorine gas.

 

In electrolysis, there are two electrodes. The negative electrode is the cathode while the positive electrode is the anode. The cathode attracts positive ions while the anode attracts negative ions. In the negative electrode, they gain electrons and are reduced while in the positive electrode, they lose electrons and get oxidised. 

 

In the negative electrode, the ions who will escape the solution depends on which one is less reactive. The less reactive one will escape while the more reactive one will stay in the solution. 

In electrolysis, electrons are shown as e^-. This is a half equation. A half equation is use to show what happens in the electrodes. A half-equation is balanced by adding, or taking away, a number of electrons equal to the total number of charges on the ions in the equation.

Positive ions gain electrons at the negative electrode, so are reduced.

• In aluminum extraction: Al³⁺ + 3e^- → Al
• In copper purification: Cu²⁺ + 2e^- → Cu
• Electrolysis of sodium chloride solution: 2H⁺ + 2e^- → H₂

Negative ions or neutral atoms lose electrons at the positive electrode and are oxidised. For example, chlorine is produced during the electrolysis of sodium chloride solution:

2Cl^- - 2e^- → Cl₂

This half-equation can be rewritten as 2Cl^- → Cl₂ + 2e^-

• In aluminum extraction: 2O^2- → O₂ + 4e^-
• In copper purification: Cu → Cu²⁺+ 2e^-

The simulation below shows what happens during the purification of copper by electrolysis.

 

Chemistry Reflection 10

Today in Chemistry, we learn about covalent bonding. Unlike in ionic bonding, the atoms cannot transfer electrons to one another so they have to share electrons. An example is Cl₂ or Cl-Cl.

 

Sometimes there can be a double or triple bonding. An example is N2. Instead of having one line between the two nitrogen. Instead there is 3 lines because it is triple bonding.

 

Compounds can contain more than one covalent bond. An example of this is methane or CH₄ which needs 4 hydrogen. It will be written as 4 lines surrounding C with H in it.