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August 13, 2020, 10:11:21 pm

Author Topic: Convert content to questions (chem)  (Read 633 times)  Share 

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insanipi

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Convert content to questions (chem)
« on: January 07, 2019, 02:20:38 pm »
+9
Hey there!

As you probably already know, practice questions are an EXTREMELY useful form of revision, and that it's generally best practice to complete them throughout the year, rather than waiting until the end; not surprisingly, this can also include making your own questions!

Remember that answering questions the way VCAA likes (such as using the provided units, showing substitution equations/working out, displaying correct # of sigfigs, and knowing key question terms) is a valuable habit to ingrain as well as understanding and knowing the content!

I'd encourage everyone to make a few questions and contribute them to this thread - if you're unsure about your question or answer post anyway (feel free to note any uncertainty) and other users will check it :)

Guidelines:
- can be of any form (diagram, multiple choice, short answer, other)
- put the answer in a spoiler
- the VCE study design, QCE syllabus and HSC syllabus  are great resources for reminding you of what topics you could write on.
« Last Edit: January 19, 2020, 11:00:32 pm by Bri MT »
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Re: Convert content to questions (chem)
« Reply #1 on: January 21, 2020, 09:11:51 pm »
+5
Atomic Theory (VCE and QCE Unit 1)
1) What is the formula for the maximum number of electrons that a shell can hold? (1)
Spoiler
A=2*n^2
For example: In shell 3, there would be 2*3^2 (2*9) electrons. That is 18 electrons.

2) Define valence electrons. (1)
Spoiler
Valence electrons are electrons that are found in the last shell that is occupied by any electrons in an atom.

3) Explain why noble gasses are called inert in relation to valence electrons. (3)
Spoiler
Noble gasses are called inert. That means that they are unreactive. (1 mark for defining the work inert.) This is due to the fact that they have a full shell of valence electrons. (1) It is the most energetically stable for an electron to have a full outer shell of electrons. (1) When an atom exists in a state where the valence shell is not completely full, it will try to gain or lose electrons in order to reach this state by reacting with other elements. Noble gasses have a full valence shell so they do not need to react in order to reach this state.

4) Write out the full electronic configuration for the element Bromide (35). (1)
Spoiler
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5 (the last number of each set of three should be written as an indice (power))

5) Explain why copper and chromium do not adhere to the Schrodinger model of the atom? (2)
Spoiler
Copper and chromium are exceptions to the Schrodinger model of the atom because of the same reason. That is, a completely full or half-full d subshell is more stable than a partially full d subshell. (1) For copper instead of having a 3d9 4s2 configuration (as expected) it has a 3s10 4s1 configuration (with a full d subshell).  For chromium instead of being 3d4 4s2 it is 3d5 4s1 so that the d shell is half full rather than partially filled.
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ArtyDreams

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Re: Convert content to questions (chem)
« Reply #2 on: January 22, 2020, 07:20:35 pm »
+6
VCE Unit 3 AOS 1

Q1. Define the term 'carbon neutral,' and provide an example of a fuel that can be classified as this.
Answer
Carbon neutral is a characteristic given to a fuel that does not result in the net production of carbon dioxide, from source or production. Bioethanol produces carbon dioxide in its formation, but the plants absorb most of this through their process of photosynthesis, meaning that bioethanol is relatively carbon neutral.

Q2. Discuss the characteristic 'hygroscopic' in relation to biodiesel.
Answer
The COO- groups in biodiesel can form hydrogen bonds with water molecules, making the substance hygroscopic. Hyroscopic is the name given to a substance that can absorb water. Therefore, biodiesel has the ability to absorb water, and can therefore be stores for a longer period of time.

Q3. Discuss the benefits of using biofuels as a source of energy production.

Answer
Biofuels are a renewable source of energy, as it is produced by plant matter. Plants grow in short time periods, meaning that the fuels can easily be replenished. Biofuels are relatively carbon neutral, as the plants take the excess carbon dioxide produced and use it for their process of photosynthesis. The production of biofuels produces less particulate matter, which is more environmentaly healthy. It is easy to source materials for their creation, as they mainly require land and water. 

Q4. In reference to the electrochemical series, when will a spontaneous reaction occur?
Answer
A spontaneous reaction will occur when the strongest oxidising agent is above the strongest reducing agent in the electrochemical series. 

Q5. What is the oxidation number of Sulfur, in Na2SO4?
Answer
The overall charge of the molecule is 0, and the charge of Na is +1, so:
(+1)(2) + x + (-2)(4) = 0
+2 + x - 8 = 0
x = 8 - 2
x = +6
Therefore, the oxidation number of sulphur is +6
 


(Mods, feel free to edit if anything doesn't make sense, I'm still a little rusty with these topics)
Also, note to anyone thinking of writing questions, or having doubts: just GO for it!! I was a little nervous going inot this, as I didn't think my knowledge was enough, but it is actually so helpful doing this! It helps you find gaps in your knowledge, but also helps enhance it. After all, if you know how examiners write questions, you're more likely to pay more detail when answering them too  ;D
« Last Edit: January 22, 2020, 07:31:13 pm by ArtyDreams »
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whys

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Re: Convert content to questions (chem)
« Reply #3 on: February 18, 2020, 12:49:58 pm »
+5
What is oxidation and reduction?
Spoiler
   - Oxidation - loss of electrons (electrons on right side of the equation)
   - Reduction - gain of electrons (electrons on left side of the equation)
Both occur simultaneously, and both must occur for the reaction to be a redox reaction
OIL RIG - Oxidation is loss, reduction is gain

What is the oxidant and reductant?
Spoiler
Oxidant/oxidising agent - cause oxidation to occur, are reduced
Reductant/reducing agent - cause reduction to occur, are oxidised

What do oxidation numbers indicate?
Spoiler
Oxidation numbers help identify if a substance has been oxidised or reduced.
Oxidation - increase in oxidation number
Reduction - decrease in oxidation number

How do you balance redox reactions in an acidic medium?
Spoiler
   - Key element (don't forget this!!!)
   - Oxygen
   - Hydrogen
   - Electrons
   - States

How do you balance redox reactions in an alkaline medium?
Spoiler
   - Key element
   - Balance oxygen atoms by adding water
   - Balance hydrogen atoms by adding H+ ions
   - Balance charge by adding electrons
   - Add hydroxide ions to neutralise H+ ions
   - Neutralisation reaction produces water, so cancel water out

What is an electrochemical cell, galvanic cell and battery?
Spoiler
Electrochemical cell: device where chemical energy is converted into electrical energy or vice versa
Galvanic cell (voltaic cell): electrochemical cell where chemical energy is converted into electrical energy
Battery: combination of cells connected to obtain a higher potential difference (voltage)

Write the oxidation and reduction half equations in a copper and zinc Daniell cell, and explain what occurs during the redox reaction.
Spoiler
• The zinc electrode corrodes because the zinc metal forms zinc ions in solution:
Zn(s) → Zn2+(aq) + 2e–
• The oxidation of the zinc metal releases electrons, which flow through the wire to the copper electrode
• Electrons are accepted by copper(II) ions in the solution when the ions collide with the copper electrode:
Cu2+(aq) + 2e– → Cu(s)
• The copper metal that is formed deposits on the electrode as a dark brown coating
« Last Edit: February 18, 2020, 07:25:38 pm by whys »