IB 화학 학교 시험 S-1 출제예상 (Stoichiometry , Line spectrum, Electron Configuration)

Question 1

When heated in air, magnesium ribbon reacts with oxygen to form magnesium oxide.

1. Write a balanced equation for the reaction that occurs. (1)
2. Identify a metal, in the same period as magnesium, that does not form a basic oxide. (1)
3. The reaction in (a)(i) was carried out in a crucible with a lid and the following data was recorded:
   • Mass of crucible and lid = 47.372 g ±0.001g
   • Mass of crucible, lid and magnesium ribbon before heating = 53.726 g ±0.001g
   • Mass of crucible, lid and product after heating = 56.941 g ±0.001g
   Calculate the amount of magnesium, in mol, that was used. (1)
4. Determine the percentage uncertainty of the mass of product after heating. (2)
5. Assume the reaction in (a)(i) is the only one occurring and it goes to completion, but some product has been lost from the crucible. Deduce the percentage yield of magnesium oxide in the crucible. (2)
6. When magnesium is burnt in air, some of it reacts with nitrogen to form magnesium nitride according to the equation:
   3Mg(s) + N₂(g) → Mg₃N₂(s)
   1. Evaluate whether this, rather than the loss of product, could explain the yield found in (b)(iii). (1)
   2. Suggest an explanation, other than product being lost from the crucible or reacting with nitrogen, that could explain the yield found in (b)(iii). (1)

Question 2

Determine the coefficients that balance the equation for the reaction of lithium with water. (1)

Li(s) + H₂O(l) → LiOH(aq) + H₂(g)

1. 0.200 g piece of lithium was placed in 500.0 cm³ of water. Calculate the molar concentration of the resulting solution of lithium hydroxide. (2)
2. Calculate the volume of hydrogen gas produced, in cm³, if the temperature was 25°C and the pressure was 101 kPa. Use sections 1 and 2 of the data booklet. (2)
3. Suggest a reason why the volume of hydrogen gas collected was smaller than predicted. (1)

Question 3

The percentage by mass of calcium carbonate in eggshell was determined by adding excess hydrochloric acid to ensure that all the calcium carbonate had reacted. The excess acid left was then titrated with aqueous sodium hydroxide.

1. A student added 27.20 cm³ of 0.200 mol dm^-3 HCl to 0.188 g of eggshell. Calculate the amount, in mol, of HCl added.
2. The excess acid requires 23.80 cm³ of 0.100 mol dm^-3 NaOH for neutralization. Calculate the amount, in mol, of acid that is in excess.
3. Determine the amount, in mol, of HCl that reacted with the calcium carbonate in the eggshell.
4. State the equation for the reaction of HCl with the calcium carbonate in the eggshell.
5. Determine the amount, in mol, of calcium carbonate in the sample of the eggshell.
6. Calculate the mass and the percentage by mass of calcium carbonate in the eggshell sample.
7. Deduce one assumption made in arriving at the percentage of calcium carbonate in the eggshell sample.

Question 4

A student added 7.40 × 10⁻² g of magnesium ribbon to 15.0 cm³ of 2.00 mol dm⁻³ hydrochloric acid. The hydrogen gas produced was collected using a gas syringe at 20.0 °C and 1.01 × 10⁵ Pa.

1. State the equation for the reaction between magnesium and hydrochloric acid. (1)
2. Determine the limiting reactant.
3. Calculate the theoretical yield of hydrogen gas:
   1. in mol (1)
   2. in cm³, under the stated conditions of temperature and pressure (1)
4. The actual volume of hydrogen measured was lower than the calculated theoretical volume. Suggest two reasons why the volume of hydrogen gas obtained was less. (2)

Question 5

Menthol is an organic compound containing carbon, hydrogen and oxygen.

Complete combustion of 0.1595 g of menthol produces 0.4490 g of carbon dioxide and 0.1840 g of water. Determine the empirical formula of the compound showing your working. (3)

0.150 g sample of menthol, when vaporized, had a volume of 0.0337 dm³ at 150 °C and 100.2 kPa. Calculate its molar mass showing your working. (2)

Question 6

A monoprotic acid, HX, is found to have the following composition by mass:

C = 39.99%
H = 6.73%
O = 53.28%

1. Determine the empirical formula of the compound HX.
2. 25.00 cm³ of a solution, containing 1.51 g of HX is titrated with a 0.750 mol dm^-3 solution of NaOH(aq). The HX(aq) solution is exactly neutralized by 22.30 cm³ of the NaOH(aq) solution. Determine the molar mass (M) of HX.
3. State the molecular formula of HX.
4. HX reacts with aqueous sodium hydroxide according to the equation:
   HX(aq) + NaOH(aq) → NaX(aq) + H₂O(l)
   Identify a functional group present in HX.

Question 7

Double salts are substances with two cations and one anion. A hydrated sulfate containing two cations has this percentage composition:

Element	Percentage (%)
Nitrogen (N)	7.09
Hydrogen (H)	5.11
Sulfur (S)	16.22
Cobalt (Co)	14.91
Oxygen (O)	---

1. 1. Draw one Lewis (electron dot) structure of the sulfate ion.
   2. Calculate the percentage of oxygen present in the double salt.
   3. Determine the empirical formula of the double salt. Use section 6 of the data booklet.
   4. The molar mass of the empirical formula is the same as the molar mass of the formula unit. Deduce the formula unit of the hydrated double salt.
2. 1.20 g of the double salt was dissolved in water and an excess of aqueous barium chloride was added, precipitating all the sulfate ions as barium sulfate.
   1. Formulate an ionic equation, including state symbols, for the reaction of barium ions with sulfate ions.
   2. Calculate the mass of barium sulfate precipitate. Use your answer to part (a)(iii) and section 6 of the data booklet. (If you did not obtain an answer for part (a)(iii), use 400.0 g mol⁻¹ as M_r for the double salt, but this is not the correct value.)

Question 8

2.478g of white phosphorus was used to make phosphine according to the equation:

P₄(s) + 3OH^-(aq) + 3H₂O(l) → PH₃(g) + 3H₂PO₂^-(aq)

1. Calculate the amount, in mol, of white phosphorus used. (1)
2. This phosphorus was reacted with 100.0 cm³ of 5.00 mol dm^-3 aqueous sodium hydroxide. Deduce, showing your working, which was the limiting reagent. (1)
3. Determine the excess amount, in mol, of the other reagent. (1)
4. Determine the volume of phosphine, measured in cm³ at standard temperature and pressure, that was produced. (1)

Question 9

The end point occurred when 3.1 ± 0.1 cm³ of the titrant had been added.

1. Calculate the percentage uncertainty associated with the titre. (1)
2. Suggest one procedural modification which would reduce the percentage uncertainty for a single titration, other than using a burette with greater precision. (1)
3. The solution in the titration flask contained 8.66 × 10^-4 g of iron. Determine, to three significant figures, the percentage of iron, by mass, in the kale leaves. (2)
4. The value obtained is about 30 times greater than published values for the percentage of iron in kale. Suggest one reason, other than human error, why there might be such a large discrepancy. (1)

Question 1

Electrons are arranged in energy levels around the nucleus of an atom.

1. Explain why the first ionization energy of calcium is greater than that of potassium. [2]
2. The diagram represents possible electron energy levels in a hydrogen atom.
1. All models have limitations. Suggest two limitations to this model of the electron energy levels. [2]
2. Draw an arrow, labelled X, to represent the electron transition for the ionization of a hydrogen atom in the ground state. [1]
3. Draw an arrow, labelled Z, to represent the lowest energy electron transition in the visible spectrum. [1]

Question 2

1. Suggest two reasons why atoms are no longer regarded as the indivisible units of matter. [2]
2. State the types of bonding in magnesium, oxygen and magnesium oxide, and how the valence electrons produce these types of bonding. [4]

   Substance	Bond Type	How the Valence Electrons Produce These Bonds
   Magnesium
   Oxygen
   MgO

Question 3

1. Most nitride ions are ¹⁴N³⁻.
1. State the number of subatomic particles in this ion. [1]
   Protons:
   Neutrons:
   Electrons:
2. Some nitride ions are ¹⁵N³⁻. State the term that describes the relationship between ¹⁴N³⁻ and ¹⁵N³⁻. [1]
3. The nitride ion and the magnesium ion are isoelectronic (they have the same electron configuration). Determine, giving a reason, which has the greater ionic radius. [1]
4. Suggest, giving a reason, whether magnesium or nitrogen would have the greater sixth ionization energy. [1]

Question 4

1. Predict, with a reason, whether Cu or Cu²⁺ has the greater ionization energy. [1]
2. Determine the frequency, in s⁻¹, of a photon that will cause the first ionization of copper. Use sections 1, 2, and 8 of the data booklet. [2]
3. Outline the magnetic properties of iron by referring to its electron configuration. [2]

Question 5

1. Consider the following reaction:
   Cu²⁺(aq) + Fe(s) → Fe²⁺(aq) + Cu(s)
   State the ground-state electron configuration for Fe²⁺. [1]
2. The mass spectrum for copper is shown:
   (Image placeholder)
   (i) Show how a relative atomic mass of copper of 63.62 can be obtained from this mass spectrum. [1]

Question 6

The periodic table is a useful tool in explaining trends of chemical behaviour.

1. (a) (i) Annotate and label the ground state orbital diagram of boron, using arrows to represent electrons. [1]

   Orbital label:

2. (a) (ii) Sketch the shapes of the occupied orbitals identified in part (a)(i). [2]

Question 7

1. (ii) Calculate the minimum frequency of light needed to break the bond in Cl₂. Use sections 1 and 2 of the data booklet. [1]

Question 8

1. (d) (i) Argon has three naturally occurring isotopes, ³⁶Ar, ³⁸Ar, and ⁴⁰Ar. Identify the technique used to determine the relative proportions of the isotopes of argon. [1]

Question 9

Fast moving helium nuclei (⁴He²⁺) were fired at a thin piece of gold foil with most passing undeflected but a few deviating largely from their path. The diagram illustrates this historic experiment.

<(a) Suggest what can be concluded about the gold atom from this experiment.

Most ⁴He²⁺ passing straight through:

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Very few ⁴He²⁺ deviating largely from their path:

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(b) (i) Subsequent experiments showed electrons existing in energy levels occupying various orbital shapes. Draw diagrams of 1s, 2s, and 2p.

1s

2s

2p

(ii) State the electron configuration of copper.

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(iii) Copper is a transition metal that forms different coloured complexes. A complex [Cu(H₂O)₆]²⁺ (aq) changes colour when excess Cl^- (aq) is added.

Explain the cause of this colour change, using sections 3 and 15 from the data booklet.

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