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Question 1

Aluminium and thallium are elements in Group 3 of the Periodic Table. Both elements form compounds and ions containing chlorine and bromine.

1. Write an equation for the formation of aluminium chloride from its elements.
2. An aluminium chloride molecule reacts with a chloride ion to form the AlCl₄⁻ ion. Name the type of bond formed in this reaction. Explain how this type of bond is formed in the AlCl₄⁻ ion.
3. Aluminium chloride has a relative molecular mass of 267 in the gas phase. Deduce the formula of the aluminium compound that has a relative molecular mass of 267
4. Deduce the name or formula of a compound that has the same number of atoms, the same number of electrons and the same shape as the AlCl₄⁻ ion.
5. Draw and name the shape of the TlBr₅²⁻ ion.
6. Draw the shape of the TlCl₂⁺ ion.
7. Explain why the TlCl₂⁺ ion has the shape that you have drawn in part (f).

Question 2

Ammonia gas readily condenses to form a liquid when cooled.

1. Name the strongest attractive force between two ammonia molecules.
2. Draw a diagram to show how two ammonia molecules interact with each other in the liquid phase. Include all partial charges and all lone pairs of electrons in your diagram.
3. Ammonia reacts with boron trichloride to form ammonia boron trichloride. Draw the molecule and state how the bond between ammonia and boron trichloride is formed.
4. The following table shows the electronegativity values of some elements.

		H	Li	B	C	O	F
	Electronegativity	2.1	1.0	2.0	2.5	3.5	4.0

 

1. Give the meaning of the term electronegativity.
2. Suggest the formula of an ionic compound that is formed by the chemical combination of two different elements from the table.
3. Suggest the formula of the compound that has the least polar bond and is formed by chemical combination of two of the elements from the table.

Question 3

Hydrogen peroxide is a very good oxidising agent.

1. Suggest a value for the H−O−O bond angle.
2. Hydrogen peroxide dissolves in water.

1. State the strongest type of interaction that occurs between molecules of hydrogen peroxide and water.
2. Draw a diagram to show how one molecule of hydrogen peroxide interacts with one molecule of water. Include all lone pairs and partial charges in your diagram.

3. Explain, in terms of electronegativity, why the boiling point of H₂S₂ is lower than H₂O₂.

Question 4

The following table shows the electronegativity values of the elements from lithium to fluorine.

		Li	Be	B	C	N	O	F
	Electronegativity	1.0	1.5	2.0	2.5	3.0	3.5	4.0

1. State the meaning of the term electronegativity.
2. Suggest why the electronegativity of the elements increases from lithium to fluorine.
3. State the type of bonding in lithium fluoride. Explain why a lot of energy is needed to melt a sample of solid lithium fluoride.
4. Deduce why the bonding in nitrogen oxide is covalent rather than ionic.
5. Oxygen forms several different compounds with fluorine.

1. Suggest the type of crystal shown by OF₂
2. Write an equation to show how OF₂ reacts with steam to form oxygen and hydrogen fluoride.
3. One of these compounds of oxygen and fluorine has a relative molecular mass of 70.0 and contains 54.3% by mass of fluorine. Calculate the empirical formula and the molecular formula of this compound. Show your working.

Question 5

Fritz Haber, a German chemist, first manufactured ammonia in 1909. Ammonia is very soluble in water.

1. State the strongest type of intermolecular force between one molecule of ammonia and one molecule of water.
2. Draw a diagram to show how one molecule of ammonia is attracted to one molecule of water. Include all partial charges and all lone pairs of electrons in your diagram.
3. Phosphine (PH₃) has a structure similar to ammonia. In terms of intermolecular forces, suggest the main reason why phosphine is almost insoluble in water.

Question 1

Aluminium and thallium are elements in Group 3 of the Periodic Table. Both elements form compounds and ions containing chlorine and bromine.

1. Write an equation for the formation of aluminium chloride from its elements.
2. An aluminium chloride molecule reacts with a chloride ion to form the AlCl₄⁻ ion. Name the type of bond formed in this reaction. Explain how this type of bond is formed in the AlCl₄⁻ ion.
3. Aluminium chloride has a relative molecular mass of 267 in the gas phase. Deduce the formula of the aluminium compound that has a relative molecular mass of 267
4. Deduce the name or formula of a compound that has the same number of atoms, the same number of electrons and the same shape as the AlCl₄⁻ ion.
5. Draw and name the shape of the TlBr₅²⁻ ion.
6. Draw the shape of the TlCl₂⁺ ion.
7. Explain why the TlCl₂⁺ ion has the shape that you have drawn in part (f).

Question 2

Ammonia gas readily condenses to form a liquid when cooled.

1. Name the strongest attractive force between two ammonia molecules.
2. Draw a diagram to show how two ammonia molecules interact with each other in the liquid phase. Include all partial charges and all lone pairs of electrons in your diagram.
3. Ammonia reacts with boron trichloride to form ammonia boron trichloride. Draw the molecule and state how the bond between ammonia and boron trichloride is formed.
4. The following table shows the electronegativity values of some elements.

		H	Li	B	C	O	F
	Electronegativity	2.1	1.0	2.0	2.5	3.5	4.0

 

1. Give the meaning of the term electronegativity.
2. Suggest the formula of an ionic compound that is formed by the chemical combination of two different elements from the table.
3. Suggest the formula of the compound that has the least polar bond and is formed by chemical combination of two of the elements from the table.

Question 3

Hydrogen peroxide is a very good oxidising agent.

1. Suggest a value for the H−O−O bond angle.
2. Hydrogen peroxide dissolves in water.

1. State the strongest type of interaction that occurs between molecules of hydrogen peroxide and water.
2. Draw a diagram to show how one molecule of hydrogen peroxide interacts with one molecule of water. Include all lone pairs and partial charges in your diagram.

3. Explain, in terms of electronegativity, why the boiling point of H₂S₂ is lower than H₂O₂.

Question 4

The following table shows the electronegativity values of the elements from lithium to fluorine.

		Li	Be	B	C	N	O	F
	Electronegativity	1.0	1.5	2.0	2.5	3.0	3.5	4.0

1. State the meaning of the term electronegativity.
2. Suggest why the electronegativity of the elements increases from lithium to fluorine.
3. State the type of bonding in lithium fluoride. Explain why a lot of energy is needed to melt a sample of solid lithium fluoride.
4. Deduce why the bonding in nitrogen oxide is covalent rather than ionic.
5. Oxygen forms several different compounds with fluorine.

1. Suggest the type of crystal shown by OF₂
2. Write an equation to show how OF₂ reacts with steam to form oxygen and hydrogen fluoride.
3. One of these compounds of oxygen and fluorine has a relative molecular mass of 70.0 and contains 54.3% by mass of fluorine. Calculate the empirical formula and the molecular formula of this compound. Show your working.

Question 5

Fritz Haber, a German chemist, first manufactured ammonia in 1909. Ammonia is very soluble in water.

1. State the strongest type of intermolecular force between one molecule of ammonia and one molecule of water.
2. Draw a diagram to show how one molecule of ammonia is attracted to one molecule of water. Include all partial charges and all lone pairs of electrons in your diagram.
3. Phosphine (PH₃) has a structure similar to ammonia. In terms of intermolecular forces, suggest the main reason why phosphine is almost insoluble in water.

1. Explain why helium’s first ionisation energy is much higher than hydrogen’s.
2. Explain why lithium has lower ionisation energy than helium even though lithium has 1 proton more.
3. Why does the main trend of first ionisation energy increase across a period?
4. Explain why the ionisation energy of aluminium is lower than that of magnesium.
5. Explain why the first ionisation of magnesium is 736 kJ mol^-1 whilst that of beryllium is 900 kJ mol^-1.
6. Explain why the second ionisation energy of sodium is much higher than the second ionisation energy of magnesium.
7. The four successive ionisation energies of beryllium are: 900 1760 1480 21000 (kJ mol^-1). Explain why there is a very big increase in ionisation energies between the second and third ionisation energies.
8. Give the group number for the following elements having these successive first ionisation energies.
   1. 799 2420 3660 25040 32850
   2. 1000 2260 3390 4540 6990 8790 27100 31700
   3. 736 1450 3740 7740 10500 1800 21700 25600
9. Which would have a greater value for the second ionisation energy: magnesium or aluminium?
10. Which would have a greater value for the third ionisation energy: magnesium or aluminium?

 

Atomic Structure

Question 1

Write the electronic configuration for: C, N^3-, Fe²⁺, Cu, Cu⁺, I and Pb.

Question 2. 

Put the following atoms/ions in order of decreasing size. Explain your answer. The atoms/ions are: Na⁺, Al³⁺, Ne, Ar, K⁺, N^3-.

Question 3:

Draw a graph representing all the ionisation energies possible for the Al atom.

Bonding

Question 1

Explain the trends in boiling points for the hydrogen halides.

Question 2

Draw the following molecules/ions: BH₂^–, NI₃, ClF₄, SF₅^–, BO₃^3-, O₃²⁺, IO₂⁺, BBr₃^2-

Energetics

Question 1

On strong heating, calcium carbonate decomposes to calcium oxide and carbon dioxide:

Owing to the conditions under which the reaction occurs, it is not possible to measure the enthalpy change directly.

An indirect method employs the enthalpy changes when calcium carbonate and calcium oxide are neutralized with hydrochloric acid.

i) Write the equation for the reaction of calcium carbonate with hydrochloric acid. State symbols are not required. [ΔH1 is the enthalpy change for this reaction]

ii) The reaction of calcium oxide with hydrochloric acid is

Use the equations in parts (i) and (ii) to complete the Hess’s Law cycle below to show how you could calculate the enthalpy change for the decomposition of CaCO₃. Label the arrows in your cycle.

Question 2

Calculate ΔH and ΔS  for the following reaction:

Use the results of this calculation to determine the value of ΔG^o for this reaction at 25^o C, and explain why NH₄NO₃ spontaneously dissolves in water at room temperature.

Compound              H_f^o(kJ mol^-1)         S(J mol^-1 K^-1)

NH₄NO₃(s)                 -365.56              151.08

NH₄⁺ (aq)                  -132.51               113.4

NO₃^– (aq)                   -205.0                 146.4

 

Equilibria

Kc

Question 1

Esters are a useful group of compounds due to their distinctive smells. One example
of an ester is ethyl ethanoate, its formation is shown below.

a) Systems like this are described as being a ‘dynamic equilibrium’. Explain
the term ‘dynamic equilibrium’

b) Write down the expression for the equilibrium constant, Kc, for this reaction.

c) Calculate the value of Kc for this reaction given the equilibrium concentrations below.

[CH₃COOH] = 0.08 moldm^-3, [C₂H₅OH] = 0.08 moldm^-3, [CH₃COO C₂H₅] = 0.25 moldm^-3, [H₂O] = 0.1 moldm^-3

d) Concentrated sulphuric acid is added to the reaction mixture as it removes water molecules. What effect would this have on the equilibrium position of this system?

Question 2

A mixture of 1.441 g of H₂ and 70.24 g of Br₂ is heated in a 2.00-L vessel at 700 K. These substances react as follows.

At equilibrium, the vessel is found to contain 0.627g of H₂. Calculate their equilibrium concentrations and Kc.

Kp

Question 1

Ammonium iodide dissociates reversibly to ammonia and hydrogen iodide.

At 400oC,Kp=0.215. Calculate the partial pressure of ammonia at equilibrium when a sufficient quantity of ammonium iodide is heated to 400oC.

Question 2

For the reaction

at 550 K, the equilibrium constant (Kp) is 9.81kPa. Suppose that 3.150 g AsCl₅ is placed in an evacuated 600 ml bulb, which is then heated to 550K.

What is the partial pressure of AsCl₅ at equilibrium? (For this question you would need to use Pv=nRT and in the ICE table, the pressure is used instead of moles)

 

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Atomic Structure
Electronic Structure
Equilibria
Energetics
Acids and Bases
Rates of Reactions
Solutions
Electrochemistry

1. how the teacher introduces scientific terminology
2. hwo the teacher uses scientific terms that students should already know
3. which language and how langugage is sued by the teacher
4. which language is sue by students and how it is used
5. any foreign students present and how these are addressed/integrated
6. any language difficultors observed, any specific anecdotes

Task 1: Use of language in the classroom

There are 8 students in the class, with all the students being Maltese, though it must be noted that whilst all the students can understand Maltese, not all of them feel comfortable speaking in Maltese. One of the students has shown some signs of struggle when the lesson was explained in Maltese as he comes from an English speaking family.

During the observed lessons, the teacher introduced a number of different concepts, including the introduction of the chapter of separating mixtures, how to write a practical and revising the chapter of solids, liquids, and gases by correcting the homework.

On introducing the chapter of separating mixtures it was immediately noted that the teacher was switching between Maltese and English, mainly to make sure that all of the students could understand the new concept and some of the new definitions. This enabled all of the students to be able to understand the concept of the new chapter, giving them a good base to understand future lessons. On explaining the concept of dissolution the teacher made a reference to the Maltese version of ‘tinhall’, which is the translation of melting. Mr Cassar explained that whilst in the Maltese language students might be using this term at home, this is not the correct terminology when it comes to chemistry.

When talking about the dissolution of gases some students could not understand how gases can dissolve in water. After trying to re-explain this concept in Maltese, as this student was more fluent in Maltese, the teacher used two short real-life examples. The first was reaffirming the simple fact that fish can breathe underwater and that therefore oxygen must have been dissolved in water. The second example was an actual story that happened to the teacher a few years prior. Whilst he was swimming he saw this metal rod underwater. Since he loved fishing he decided to dive and get the rod to the surface, expressing his relief that the rod had not rusted. The following morning this rod had rusted, showing that whilst oxygen can dissolve in water, this is not done in large amounts.

When analysing the most common mistakes found in the homework the teacher spoke only in Maltese, as this was the language that both him and most of his students feel most comfortable with. This allowed the teacher to help students understand what they did wrong and what could have been done better in a way they could understand. In fact, it was easily noticeable that all students, irrespective of their mark in the homework, felt that they were satisfied with the explanation, and left the classroom knowing that next time, they could do better.

After the lesson, I had a meeting with my mentor and we had a small discussion about the language used in classroom. This allowed me to be able to discern on the language used in my classroom, especially in the areas where I differ from the teacher that I was observing. During the conversation, I questioned the use of the Maltese language during the lesson, especially when considering that the exam will be in English. My mentor pointed out that whilst the exam is in English it is important that the students first understand the concepts prior to being able to answer questions in an exam. In fact, after this conversation I realised hat code-switching from Maltese to English and vice versa should not be frowned upon during a lesson, but rather be used as a tool to ensure that all students are given the same opportunities to understand all the concepts that I am putting forward during the lesson.

1) Dr Spiteri discusses nine dimensions that influence school climate. What are they, and how do these relate to the KIPP schools he mentions earlier?

The school climate is the quality and character of school life. As seen in the Maltese environment there seems to be a correlation between the school climate and the performance of students, with better environment resulting in higher grades. The removal of the junior lyceum exams seems to be motivated to try and establish all governmental schools to try and have a similar school climate.

The 9 dimensions as discussed in the video are:

• Clarity: The students should know what is being expected of them
• Fairness: Every student expects to be treated equally
• Environment: This is the place where students will spend most of their times, therefore this will need to be clean and comfortable.
• Interest: A student should be motivated when they go to school.
• Order: A nurturing environment for students to grow.
• Participation: students should be encouraged to participate in class.
• Standards: There should be a high expectation for all students.
• Safety: When at school, students have the right to feel safe.
• Support: A student should know that at school there is a support system in place for whatever is necessary, especially with regards to encouragement and guidance.

These 9 dimensions are crucial in KIPP schools, which are a set of American schools that offer free education to students who come from poorer backgrounds. In fact, 95% of students come from Afro-American or Hispanic families. These schools provide a climate for students to be able to get the grades to go to college, with the whole system being set up to provide the perfect environment for these students to succeed.

2) Prof. Darmanin discusses five key factors that contribute to a positive learning environment and allow secondary school students to learn, and learn well. What are these, and how are they related to the dimensions of school climate discussed earlier by Dr. Spiteri?

Professor Darmanin starts her vidcast emphasising that students want to learn. This is very important, cos when the students are willing then it will be the students themselves who demand that they are thought in a positive manner.

The five key factors mentioned by Prof Darmanin are:

• Teacher order and discipline: Students want to be in an environment where they are allowed to learn.
• Work should be demanding and salient: The work done should be challenging and should make students think about what they are doing.
• Lessons should have a good pace: Students want to learn something new all the time, and it is important not to spend too much time saying the same thing.
• Students do not want to be bored: A bored student is a student who is not loving the lesson and therefore a student who is not learning.
• Subjects should be horizontally connected: whatever a student is learning should be seen and understood in a wider context and not just for that one particular subject.

In fact, in other terms, it could be said that students want to have a classroom climate where they can learn. These seem to be extensions of what Dr Spiteri said in his vidcast where he mentioned a number of different dimensions that affect the school climate. If the school climate is not good and does not nurture learning than it would be very difficult to have a positive learning outcome, even if all the factors mentioned by Prof Darmanin are in place.

The Ionisation Energy is the energy require to remove an electron from a gaseous atom or ion at stp.

There can be multiple ionisation energies, such as:

First Ionisation Energy: Energy required to remove an electron from a gaseuos atom to form a uni-positive ion.

 

 

The periodic table contains a lot of information. The numbers of the neutrons, electrons and protons can all be found using such information.

Proton Number = Atomic number

Neutron Number = Mass number – Atomic Number

Electron Number =  Atomic Number – Charge

Once the number of electrons has been established these should be drawn into shells (For information on how to place electrons into orbitals please read more in Atomic Structure).

Each shell can take up a number of different electrons, but for the intents of this chapter the first shell takes in 2 electrons, the second shell takes in 8 electrons, the third shell takes in 8 electrons and the in the fourth shell the maximum number of electrons that will be put in it is going to be 2 electrons.

For example:

Oxygen has 8 electrons, therefore these will be placed in shells as 2 in the first shell, and 6 in the second shell, being written as 2, 6.

Calcium has 20 electrons, therefore these will be placed in shells as 2 in the first shell, 8 in the second shell, 8 in the third shell and the final 2 in the fourth shell, being written as 2, 8, 8, 2.

In order to draw these atoms with electrons around them, one should draw the nucleus, either as the letter of the element or the number of protons and neutrons, and shells around it. The electrons are then depicted as either dots or crosses.

Putting Electrons in Shells