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Test your knowledge

Sample questions for a general chemistry course

 

Chapter 1

Why is chem istry known as a fundamental science?

How does chemistry differ from physics?

Back in the 1960s, in what stage of its development did classical chemistry stop? What had been the next tasks to resolve?

What kind of experiments resulted in the refusal of traditional (classical) explanations of chemical phenomena and caused the emergence of quantum chemistry? How were these experiments explained after returning to the classic model?

 

Chapter 2

Write the symbols of the first three periods from the table of elements.

Name these elements.

To which groups do the following elements belong: K, Si, Ca, S, Mg, He, Cl?

What role is played in chemistry by the electrons, the atoms' outermost shells, and the electrons' innermost shells?

  What is the role of the atom's nucleus in chemistry? Explain the essence of ionization energy.

Explain what is meant by the ionization energy of an electron in an atom.   

 What does FIE stand for? How many electrons are there in the outermost layers of elements №5, № 10, №12 and №14?

How many protons are there in the nuclei of atoms?

What is the table of elements?

Explain the manner in which the table of elements is constructed.

Write out the table of elements for the first 20 elements.

Explain how the number of electrons in each electron layer is determined.

On the basis of what experimental data can we define the maximal amount of electrons that can be situated by the first 20 elements of the table of elements?

 

What do we mean by the affinity of atoms to the electron?

Which data on the affinity of atoms towards electrons prove the correctness of this model?

On the basis of what data do we draw the conclusion that bonding electrons rotate on a plane perpendicular to the axis that connects bonded nuclei?

Which electrons are regarded as bonding electrons?

Generally, when we move from one element to another from left to right in the table of elements (2nd and 3rd periods), the FIE changes. Are there any exceptions to this rule?

What data on the affinity of the atoms to the electrons explain these exceptions?

What elements are regarded as anomalous from the point of view of bonding theory?

What is an anomalous element in the physical and chemical sense? Why is its behavior anomalous?

Name the groups of anomalous elements. How do they differ? Give some examples.

 

Chapter 3        

Write the structural formulas of the following compounds: SO2, SO3, NO2, HClO, XeO, CH4, NaCl.

At the expense of energy from what source (nuclei or electrons) does the energy gain occur?

Why is there an energy gain during bond formation? Explain this qualitatively and quantitatively.

Write an equation with which we can calculate the bonding energy in a hydrogen molecule.

What approximations are necessary to calculate the bonding energies of dual-atomic molecules besides H2? Explain dual-atomic molecules formed of atoms with close FIEs or of atoms with differing FIEs.

Why do we actually need much more energy than the calculation requires for the breaking of the bond in a hydrogen molecule? Find how much more energy is required.

How is a hydrogen molecule formed?

Where do we find the contradiction between the offered chemical bonding model in a hydrogen molecule and the data on the affinity of hydrogen atoms towards electrons?

Why, for a thermal breaking of a chemical bond in the hydrogen molecule, is greater energy needed than for the ionization of the molecule?

 

Chapter 4

How do dynamic chemical bonds differ from covalent bonds and DABs?

How is a covalent homoatomic bond formed? How is a heteroatomic bond formed?

How does the energy of a covalent homoatomic and heteroatomic bond depend on the FIEs of the atoms being bonded?

How does the length of a covalent homoatomic bond depend on the FIEs of the atoms being bonded?

What other bonds (besides covalent ones) do you know?

What is the physical essence of DABs and VWBs?

What is the valence of an element?

How many chemical bonds (covalent and DABs) can an element form?

Why is it that when an atom is connected with various types of bonds to identical atoms, the bonds equalize their energy and length?

What is electronic isomerization? Give some examples. How is the speed of electronic nuclear isomerization defined? What phenomenon does this reaction explain?

What experimental facts speak to the effect that two (rather than one or three) electrons take part in the formation of a covalent bond?

What experimental facts confirm the correctness of the theory of chemical bonding?  

Explain the meaning of the term "valence."

How is the valence determined in elements of the I, II, III and IV groups?

How do we define the valence in elements of the V, VI, VII, and VIII groups?

What is valence relative to hydrogen?

Construct a chemical bonding model based on the comparison of the number of electrons in the outermost layers of the first 20 elements and the data on their valence.

What are the main forces in the creation of a chemical bond?

What experiments and calculations prove this?

What justifies a one-electron approximation, how does it manifest itself and for what calculations has it been used?

For the first twenty elements, what is the correlation between the valence of the element and its group?

Why is the removal of valence electrons from an atom easier than the removal of core electrons?

Why is it easier for electrons inside the molecule to absorb energy by fewer portions than for electrons inside the atom?

 

Chapter 5

Define the time of electronic transition if the reaction D + H2 → DH + H occurs in one second.

What is the limiting stage of a reaction?

Why does this stage define the speed of the reaction?

Give some examples from everyday life.

 

Explain why, to break the chemical bond in a hydrogen molecule, the molecule must be heated to 3000 degrees, while, in a presence of Chlorine atoms, the bond breaks at 30 degrees. Explain why the energy needed for breaking the chemical bond in a hydrogen molecule with a photochemical reaction or an electron bombardment is two times less than that needed for the thermal breaking of the bond.

Write reaction mechanisms for the following reactions: 

a) Cl2 + H2=2 HCl;

b) Cl2 + I2=2 HI ;

c)Cl2+2KBr=2KCl+Br2;

d) Ether + H2O = alcohol + acid;

name the main stages of these reactions,

explain why aren't they running using a molecular mechanism;

choose an efficient way to increase the rate of these reactions from the following:

exposure to radiation, a catalyst, a solvent or heating;

explain the role of water in reaction c);

explain the role of radiation in reaction a);

explain the role of catalyst in reaction d).

 

Why do we need a spark plug in a car?

Why do the contents of exhausted gas need to be checked up?

How is the exhaust gas of a car cleaned?

 

Chapter 6

Give three examples of physical and chemical properties of substances.

Offer 3 proofs of the fact that only electrons of the outermost layer are responsible for the chemical and physical properties of elements.

Explain why the exchange period in the main properties of the first 20 elements is equal to 8, while the valence via hydrogen (the main chemical property) has an exchange period equal to 4.

Give some examples from physics or chemistry confirming or negating the correctness of the statements given below.

 

Why are the Lewis Rules referred to as "rules"?

What is the difference between facts, rules, laws, and theories? Give some examples.

What stable compounds are exceptions to the Lewis Rules?