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Date	May 2018	Marks available	1	Reference code	18M.2.sl.TZ1.2
Level	SL	Paper	2	Time zone	TZ1
Command term	Estimate	Question number	2	Adapted from	N/A

Question

Calcium carbide, CaC₂, is an ionic solid.

Describe the nature of ionic bonding.

[1]

State the electron configuration of the Ca²⁺ ion.

[1]

When calcium compounds are introduced into a gas flame a red colour is seen; sodium compounds give a yellow flame. Outline the source of the colours and why they are different.

[2]

Suggest two reasons why solid calcium has a greater density than solid potassium.

[2]

d.i.

Outline why solid calcium is a good conductor of electricity.

[1]

d.ii.

Calcium carbide reacts with water to form ethyne and calcium hydroxide.

CaC₂(s) + H₂O(l) → C₂H₂(g) + Ca(OH)₂(aq)

Estimate the pH of the resultant solution.

[1]

Markscheme

electrostatic attraction AND oppositely charged ions

[1 mark]

1s²2s²2p⁶3s²3p⁶

[Ar]

[1 mark]

«promoted» electrons fall back to lower energy level

energy difference between levels is different

Accept “Na and Ca have different nuclear charge” for M2.

[2 marks]

Any two of:

stronger metallic bonding

smaller ionic/atomic radius

two electrons per atom are delocalized

greater ionic charge

greater atomic mass

Do not accept just “heavier” or “more massive” without reference to atomic mass.

[2 marks]

d.i.

delocalized/mobile electrons «free to move»

[1 mark]

d.ii.

pH > 7

Accept any specific pH value or range of values above 7 and below 14.

[1 mark]

Examiners report

[N/A]

d.i.

[N/A]

d.ii.

[N/A]

Syllabus sections

Core » Topic 3: Periodicity » 3.2 Periodic trends

Show 78 related questions

18M.1.sl.TZ1.7: Which describes the oxide of sodium, Na2O?
18M.1.sl.TZ1.8: Which statement is correct? A. Atomic radius decreases down group 17. B. First...
18M.1.sl.TZ2.7: Which increase across a period from left to right?
18M.2.sl.TZ2.3b.ii:
Outline why the ionic radius of K⁺ is smaller than that of Cl⁻.
18M.2.sl.TZ2.3b.i:
Outline why atomic radius decreases across period 3, sodium to chlorine.
22M.2.sl.TZ2.1d: Describe two observations that indicate the reaction of lithium with water is exothermic.
22M.2.hl.TZ1.5d(iv): The polarity of the carbon–halogen bond, C–X, facilitates attack by HO–. Outline, giving a...
17N.2.sl.TZ0.2a: Explain the general increasing trend in the first ionization energies of the period...
17N.1.sl.TZ0.8: Which oxide dissolves in water to give a solution with a pH below 7? A. MgO B. Li2O C....
22M.2.hl.TZ1.1a(ii): Identify a metal, in the same period as magnesium, that does not form a basic oxide.
22M.2.hl.TZ1.1e(iii):
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.
16N.2.sl.TZ0.4d: Describe the trend in acid-base properties of the oxides of period 3, sodium to chlorine.
22M.1.sl.TZ2.7: Three elements, X, Y, and Z are in the same period of the periodic table. The relative sizes...
17M.1.sl.TZ2.12: Which metal has the strongest metallic bond? A. Li B. Na C. K D. Rb
17M.1.sl.TZ1.8: Which oxide, when added to water, produces the solution with the highest pH? A. Na2O B....
16N.1.sl.TZ0.8:
Which solution forms when phosphorus(V) oxide, P₄O₁₀, reacts with water?
22M.1.hl.TZ2.6: Which are the most reactive elements of the alkali metals and halogens? A. Lithium and...
22M.1.hl.TZ2.5: What is the correct order for increasing first ionization energy? A. Na < Mg <...
19M.2.hl.TZ2.4e(i):
Suggest why the existence of salts containing an ion with this formula could be predicted. Refer to section 6 of the data booklet.
22M.2.sl.TZ2.2a:
Explain why the first ionization energy of calcium is greater than that of potassium.
18M.2.sl.TZ1.2d.i:
Suggest two reasons why solid calcium has a greater density than solid potassium.
21N.1.sl.TZ0.7: Which element has the highest metallic character in Group 14? A. C B. Si C. Ge D. Sn
21N.1.sl.TZ0.8: Which combination describes the acid–base nature of aluminium and phosphorus oxides?
18N.1.sl.TZ0.7: Which oxides produce an acidic solution when added to water? I. Al2O3 and SiO2 II. ...
18N.1.sl.TZ0.8: Which species will require the least energy for the removal of one electron? A. ...
18N.2.hl.TZ0.4a: Explain the decrease in atomic radius from Na to Cl.
18N.2.sl.TZ0.4a: Explain the decrease in atomic radius from Na to Cl.
18N.2.hl.TZ0.4b: Explain why the radius of the sodium ion, Na+, is smaller than the radius of the oxide ion, O2−.
18N.2.sl.TZ0.4b.i: Explain why the radius of the sodium ion, Na+, is smaller than the radius of the oxide ion, O2−.
17M.1.hl.TZ1.6: What is the order of decreasing ionic radius? A. S2− > Cl− > Al3+ > Mg2+ B. ...
16N.1.hl.TZ0.7: Which property increases down group 17, the halogens? A. Electron affinity B. Boiling...
19M.1.hl.TZ1.7: Which series represents atoms in order of decreasing atomic radius? A. N > C > Be >...
16N.1.hl.TZ0.8: Which correctly describes the reaction between potassium and excess water? A. The reaction...
19M.3.hl.TZ1.1b(iv):
Sketch how the first ionization energies of elements vary with their atomic radius.
19M.3.sl.TZ1.1b(iv):
Sketch how the first ionization energies of elements vary with their atomic radius.
19M.1.sl.TZ1.8: What are typical characteristics of metals?
19M.1.sl.TZ2.8: How do the following properties change down Group 17 of the periodic table?
17M.2.sl.TZ2.1c.i:
Some oxides of period 3, such as Na₂O and P₄O₁₀, react with water. A spatula measure of each oxide was added to a separate 100 cm³ flask containing distilled water and a few drops of bromothymol blue indicator.

The indicator is listed in section 22 of the data booklet.

Deduce the colour of the resulting solution and the chemical formula of the product formed after reaction with water for each oxide.
17N.1.sl.TZ0.7:
Which trends are correct across period 3 (from Na to Cl)?

I. Atomic radius decreases
II. Melting point increases
III. First ionization energy increases

A. I and II only

B. I and III only

C. II and III only

D. I, II and III
17M.1.hl.TZ2.5: X, Y and Z represent the successive elements, Ne, Na and Mg, but not necessarily in that...
17M.2.sl.TZ1.2d.ii:
Explain why an aluminium-titanium alloy is harder than pure aluminium.
19N.1.sl.TZ0.7: Which property shows a general increase from left to right across period 2, Li to F? A. ...
16N.2.sl.TZ0.4e:
In addition to magnesium oxide, magnesium forms another compound when burned in air. Suggest the formula of this compound
17N.2.sl.TZ0.2c:
State an equation for the reaction of phosphorus (V) oxide, P₄O₁₀ (s), with water.
17M.2.hl.TZ1.2d.ii:
Suggest why the melting point of vanadium is higher than that of titanium.
21N.1.hl.TZ0.6: Which ion has the largest radius? A. Na+ B. Mg2+ C. P3− D. S2−
18M.2.hl.TZ1.2d.i:
Suggest two reasons why solid calcium has a greater density than solid potassium.
17N.2.sl.TZ0.2b:
Explain why the melting points of the group 1 metals (Li → Cs) decrease down the group.
19M.2.hl.TZ1.3b:
Outline why the alkali metals (group 1) have similar chemical properties.
19M.2.sl.TZ2.4a:
Before its isolation, scientists predicted the existence of rhenium and some of its properties.

Suggest the basis of these predictions.
21M.1.sl.TZ1.8: Which trend is correct, going down group 1? A. Melting point increases B. Reactivity...
19N.2.sl.TZ0.6b:
Another airbag reactant produces nitrogen gas and sodium.

Suggest, including an equation, why the products of this reactant present a safety hazard.
16N.1.sl.TZ0.7:
Which equation represents the first electron affinity of chlorine?

A. Cl(g)+e^-→ Cl^-(g)
B. $\frac{1}{2}$ Cl₂(g) + e^- → Cl^-(g)
C. Cl⁺(g) + e^- → Cl(g)
D. Cl(g) → Cl⁺(g) + e^-
17N.2.hl.TZ0.3b:
Explain why the melting points of the group 1 metals (Li → Cs) decrease down the group whereas the melting points of the group 17 elements (F → I) increase down the group.
20N.1.hl.TZ0.6: What is the correct trend going down groups 1 and 17? A. Melting points increase B. Boiling...
19M.2.hl.TZ1.3e:
Write equations for the separate reactions of solid sodium oxide and solid phosphorus(V) oxide with excess water and differentiate between the solutions formed.

Sodium oxide, Na₂O:

Phosphorus(V) oxide, P₄O₁₀:

Differentiation:
22M.1.sl.TZ1.7: Which gases are acidic? I. nitrogen dioxideII. carbon dioxideIII. sulfur dioxide A. I...
22M.1.sl.TZ1.8:
Which of the following is the electron configuration of a metallic element?

A. [Ne] 3s² 3p²

B. [Ne] 3s² 3p⁴

C. [Ne] 3s² 3p⁶ 3d³ 4s²

D. [Ne] 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵
19M.2.sl.TZ1.3a(ii):
Write equations for the separate reactions of solid sodium oxide and solid phosphorus(V) oxide with excess water and differentiate between the solutions formed.

Sodium oxide, Na₂O:

Phosphorus(V) oxide, P₄O₁₀:

Differentiation:
19M.2.hl.TZ2.3b(iii):
Predict, giving two reasons, how the first ionization energy of ¹⁵N compares with that of ¹⁴N.
19M.2.sl.TZ2.3c:
Suggest why it is surprising that dinitrogen monoxide dissolves in water to give a neutral solution.
21M.2.hl.TZ1.1d(iv):
Outline, in terms of their electronic structures, why the ionic radius of the sulfide ion is greater than that of the oxide ion.
21M.1.sl.TZ2.7: Which property increases down group 1? A. atomic radius B. electronegativity C. first...
21M.2.sl.TZ1.1c(iii):
Outline, in terms of their electronic structures, why the ionic radius of the sulfide ion is greater than that of the oxide ion.
21M.2.sl.TZ2.2a(i): Explain why Si has a smaller atomic radius than Al.
20N.1.sl.TZ0.7:
Which of the following shows a general increase across period 3 from $Na$ to $Cl$ ?

A. Ionic radius

B. Atomic radius

C. Ionization energy

D. Melting point
21M.2.hl.TZ2.2a(i): Explain why Si has a smaller atomic radius than Al.
20N.2.sl.TZ0.1a(ii):
State, giving a reason, whether the chlorine atom or the chloride ion has a larger radius.
20N.1.sl.TZ0.8:
Which oxide will dissolve in water to give the solution with the lowest pH?

A.   $P_{4} O_{10}$

B.   ${SiO}_{2}$

C.   ${Al}_{2} O_{3}$

D.   $MgO$
20N.2.hl.TZ0.1a(iii):
Outline why the chlorine atom has a smaller atomic radius than the sulfur atom.
20N.2.hl.TZ0.1a(ii):
State, giving a reason, whether the chlorine atom or the chloride ion has a larger radius.
20N.2.sl.TZ0.1a(iii):
Outline why the chlorine atom has a smaller atomic radius than the sulfur atom.
18M.2.hl.TZ1.2f:
Calcium carbide reacts with water to form ethyne and calcium hydroxide.

CaC₂(s) + H₂O(l) → C₂H₂(g) + Ca(OH)₂(aq)

Estimate the pH of the resultant solution.
22M.2.sl.TZ1.1a(iii): Identify a metal, in the same period as magnesium, that does not form a basic oxide.
22M.2.sl.TZ1.1e(iii):
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.
22M.2.sl.TZ1.3f(iii): The polarity of the carbon–halogen bond, C–X, facilitates attack by HO–. Outline, giving a...
21N.2.hl.TZ0.2a: Explain the general increase in trend in the first ionization energies of the period 3...
21N.2.sl.TZ0.2: Explain the general increase in trend in the first ionization energies of the period 3...

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