Bonding Flashcards
Magnesium sulphate is an ionic compounds
with reference to its bonding explain whether you would expect magnesium sulphate to have a high or low melting point
Magnesium sulphate is an ionic compound so will have a giant ionic lattice structure where the ions are held together by a very strong electrostatic forces these bonds require a lot of energy to break some magnesium sulphate will have a very high melting point
What is sulphate compound ion formula
SO42-
Gives the formula of ammonium
NH4 plus
What effect does electrostatic attraction have on oppositely charged ion
It holds positive and negative ions together
Explain what an ionic lattice is
A regular structure made up of ions
Draw the structure of sodium chloride showing at least 12 ions
Cjck
Explain why ionic compounds conduct electricity when molten
The ions in the liquid are free to move and carry charge
Magnesium oxide is an ionic compound apart from electrical conductor conductivity when molten or dissolved describe to physical properties you would expect magnesium oxide to have
It should have a high melting points and dissolve in water
Hydrogen peroxide dissolves in water state the strongest type of interaction that occurs between molecules of hydrogen peroxide and water
Hydrogen bonding
Explain in terms of electronegativity why the body and boiling points of H2S2 is lower than H202
The electronegativity of S is lower than O
is no hydrogen bonding between H2S2 molecules only Vanderwall’s
States the meaning of the term electronegativity
The power of an atom to withdraw or attract electrons
Suggest why the electronegativity of the elements increase from lithium to fluorine
More protons bigger nuclear charge
State the type of bonding in lithium fluoride explain why a lot of energy is needed to melt a small sample of solid lithium fluoride
Bonding : ionic
Explanation : Strong or many electrostatic attraction between + and - ions
Whys is the bonding nitrogen oxide is covalent rather than ionic
Small electronegativity difference
oxygen forms several different compounds with FluorineSimple molecular suggest the type of crystal shown by OF2
Simple molecular
Write an equation to show how OF2 reacts with steam to form oxygen and hydrogen fluoride
O2 + H2O —> O2 + 2HF
One of these compounds of oxygen and flooring has a relative molecular mass of 70 and contains 54.3% by mass of fluorine calculate the empirical formula and the molecular formula of this compound
Empirical formula : start with % , 54.3% is F so 45.7 is O2
Divide each % by the relative mass of each you should get 2.85 for F
and 2.85 for O
ratio of 1 to 1
so empirical formula is just FO
Molecular formula: as for molecular formula it would be F202 as the molecular mass of that molecule is 70
Ammonia gas readily condenses to form a liquid when cooled
name the strongest attractive force between two ammonia molecules
H bonds
Ammonia reacts with boron trichloride to form a molecule with the following structure
state how the bonds between ammonia and boron trichloride is formed
Electron pair on the ammonia is donated to boron trichloride
ethanedioic acid is a weak acid ethanedioic acid acts initially as a monoprotic acid
use the concept of electronegativity to justify why the acid strengths of ethanedioic and ethanoic acid are different
Both acids contain A carboxylic acid group however in ethanoic acid R=CH3 and ethanedioic acid and carboxylic acid
The oxygen atom in the carboxylic acid group of ethanedioic acid are highly electronegative so draw electrons towards them from the neighbouring carboxylic acid
causes the hydroxyl group to become more polarised
this makes bond fission more likely
so hydrogen ions More likely to dissociate.
in ethanoic acid the CH3 group is not electron drawing so has no effect on hydroxide polarity ethanedioic is therefore a stronger acid than ethanoic acid
A buffer solution is made by adding 6.00 × 10–2 mol of sodium hydroxide to a
solution containing 1.00 × 10–1 mol of ethanedioic acid (H
Assume that the sodium hydroxide reacts as shown in the following equation and that in this buffer solution, the ethanedioic acid behaves as a monoprotic acid.
H2C2O4(aq) + OH–(aq)—->HC2O4–(aq)+H2O(l)
The dissociation constant Ka for ethanedioic acid is 5.89 × 10–2 mol dm–3.
Calculate a value for the pH of the buffer solution.
Give your answer to the appropriate number of significant figures.
Moles of NaOH = Moles of HOOCCOO– formed = 6.00 × 10–2
Moles of HOOCCOOH remaining = 1.00 × 10–1 – 6.00 × 10–2 = 4.00 × 10–2
Ka =[H+][A–]/[HA]
[H+]=Ka ×[HA]/[A–]
[H+]=5.89×10–2 ×(4.00×10–2 /V)/(6.00×10–2 /V)=3.927×10–2
pH = –log10(3.927 ×10–2) = 1.406= 1.41
In a titration, the end point was reached when 25.0 cm3 of an acidified solution containing ethanedioic acid reacted with 20.20 cm3 of 2.00 ×10–2 mol dm–3 potassium manganate(VII) solution.
Deduce an equation for the reaction that occurs and use it to calculate the original concentration of the ethanedioic acid solution.
Equation ……………………………………………………………………………………………
Original concentration = …………………………. mol dm-3
5H2C2O4 + 6H+ + 2MnO4– 2Mn2+ + 10CO2 + 8H2O
OR 5C2O42– + 16H+ + 2MnO4– 2Mn2+ + 10CO2 + 8H2O Page 7
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Stage 1: difference in structure of the two acids • The acids are of the form RCOOH
• but in ethanoic acid R = CH
• whilst in ethanedioic acid R = COOH
Stage 2: the inductive effect
• The unionised COOH group contains two very electronegative oxygen
atoms
• therefore has a negative inductive (electron withdrawing)effect
• The CH 3
group has a positive inductive (electron pushing) effect
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(c)
PhysicsAndMathsTutor.com
Moles of KMnO4 = 20.2 × 2.00 × 10–2 / 1000 = 4.04 × 10–4
Moles of H2C2O4 = 5 / 2 × 4.04 × 10–4 = 1.01 × 10–3
Concentration = moles / volume (in dm3) =1.01×10–3 ×1000/25=4.04×10–2 (moldm–3)
If 1:1 ratio or incorrect ratio used, M2 and M4 can be scored
Silicon dioxide (SiO2) has a crystal structure similar to diamond.
Give the name of the type of crystal structure shown by silicone dioxide
Suggest why silicon dioxide does not conduct electricity when molten. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
Silicon dioxide reacts with hydrofluoric acid (HF) to produce hexafluorosilicic acid (H2SiF6) and one other substance.
Write an equation for this reaction.
Giant covalent
No delocalised electrons
SiO2 + 6HF H2SiF6 + 2H2O
Some airbags in cars contain sodium azide (NaN3).
(a)
Sodium azide is made by reacting dinitrogen monoxide gas with sodium amide (NaNH2) as shown by the equation.
2NaNH2 + N2O NaN3 + NaOH + NH3
Calculate the mass of sodium amide needed to obtain 550 g of sodium azide, assuming there is a 95.0% yield of sodium azide.
Give your answer to 3 significant figures.
……………………………………………………………………..
550 x 100/95
So 100% would b 8.46 x 100/95 = 8.91 moles of NaN3
Then M3 Moles NaNH2 = 8.91 × 2 = ( 17.8(2) moles)
M4 mass NaNH2 = 17.8(2) × 39 M5 693 (g)
Nitrous acid decomposes on heating.
Balance the following equation for this reaction.
ii) 3HNO2 HNO3 + 2NO + H2O
Sodium azide has a high melting point.
Predict the type of bonding in a crystal of sodium azide. Suggest why its melting point is high.
Type of bonding ………………………………………………………………………………… Reason for high melting poin
Ionic
Oppositely charged ions
Strong attraction between (oppositely charged) ions
Give the formula of a molecule that has the same number of electrons as the azide ion.
…………………
t formula of magnesium azide?
CO2
MgN6
The structure of the bromoalkane Z is
Give the IUPAC name for Z.
Give the general formula of the homologous series of straight-chain bromoalkanes
that contains one bromine atom per molecule.
Suggest one reason why 1-bromohexane has a higher boiling point than Z. ………………………..
2-bromo-2,3-dimethylbutane
CnH2n+1Br
Stronger / more vdw (forces) between molecules (of 1-bromohexane)
Nickel is a metal with a high melting point.
(i) State the block in the Periodic Table that contains nickel.
…………………………………………………………………………………….
D block
Explain, in terms of its structure and bonding, why nickel has a high melting point.
………..
ii) Contains positive (metal) ions or protons and delocalised electrons
Strong attraction between them or st
Explain why nickel is ductile (can be stretched into wires).
s / sheets of atoms or ions can slide over one another
i) Give the full electron configuration of the Ni2+ ion.
1s2 2s2 2p6 3s2 3p6 3d8 (4s0)
Balance the following equation to show how anhydrous nickel(II) chloride can
be obtained from the hydrated salt using SOCl
Identify one substance that could react with both gaseous products.
…NiCl2.6H2O(s) + …SOCl2(g)—->…NiCl2(s) + …SO2(g) + …HCl(g)
Substance …………………
NiCl2.6H2O + 6 SOCl2 —> NiCl2 + 6 SO2 + 12 HCl
NaOH / NH3 / CaCO3 / CaO
NiCl2 + 6 SO2 + 12 HCl
Allow any name or formula
Q5.In 2009 a new material called graphane was discovered. The diagram shows part of a model of the structure of graphane. Each carbon atom is bonded to three other carbon atoms and to one hydrogen atom.
Deduce the type of crystal structure shown by graphane. ………………………………………………………………………………………..
State how two carbon atoms form a carbon–carbon bond in graphane.
Giant covalent
Shared pair of e-‘s
Suggest why graphane does not conduct electricity.
No delocalised electrons
d) Deduce the empirical formula of graphane.
CH
Thallium(I) bromide (TlBr) is a crystalline solid with a melting point of 480 °C.
(b)
Suggest the type of bonding present in thallium(I) bromide and state why the melting point is high.
…..
Ionic
M2 Oppositely charged ions / Tl+ and Br− ions
M3 Strong attraction between ions
Write an equation to show the formation of thallium(I) bromide from its elements.
Tl + 1/2Br2 —-> TlBr
Q1.Which type of bond is formed between N and B when a molecule of NH3 reacts with a molecule of BF3? A Ionic. B Covalent. C Co-ordinate. D Van der Waal
C
Ammonia gas readily condenses to form a liquid when cooled.
(i) Name the strongest attractive force between two ammonia molecules.
H bonds
Predict the bond angle in the PH4 + ion. ………………………………………………
109.5°c
Although phosphine molecules contain hydrogen atoms, there is no hydrogen bonding between phosphine molecules.
Suggest an explanation for this.
(1)
……………………………………………………..
Difference in electronegativity between P and H is too small
Aluminium and thallium are elements in Group 3 of the Periodic Table.
Both elements form compounds and ions containing chlorine and bromine.
Write an equation for the formation of aluminium chloride from its elements.
Al + 1.5Cl 2 → AlCl3
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
Explanation ………………………………………………………………………………………. ………………………………………………………………………………………………………… …………………………………………………………………………………………………………
Type of bond ………………
Coordinate
Electron pair on cl- donated to al(cl3)
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
…………
Al2Cl6
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 AlCl − 4
ion. …………………………………………………………………………………………………..
SiCl4
Explain why the TlCl2+ ion has the shape that you have drawn
Two) bonds (pairs of electrons) repel equally
Which one of the first, second or third ionisations of thallium produces an ion with the electron configuration [Xe] 5d106s1?
Second
Which compound has the highest boiling point?
A C2H4
B C2H6
C CH3NH2
D CH3F
C
Ethanol can be oxidised by acidified potassium dichromate(VI) to ethanoic acid in a two-step process.
(a)
ethanol ethanal ethanoic acid
In order to ensure that the oxidation to ethanoic acid is complete, the reaction is carried out under reflux.
Describe what happens when a reaction mixture is refluxed and why it is necessary, in this case, for complete oxidation to ethanoic acid
A mixture of liquids is heated to boiling point for a prolonged time
Vapour is formed which escapes from the liquid mixture, is changed back into liquid and returned to the liquid mixture
Any ethanal and ethanol that initially evaporates can then be oxidised
Write a half-equation for the overall oxidation of ethanol into ethanoic acid.
CH3CH2OH + H2O CH3COOH + 4H+ + 4e–
your understanding of intermolecular forces to predict which of these compounds has the highest boiling point.
A HF
B HCl
C HBr
D HI
A
Which of these substances does not show hydrogen bonding? A HF B NH3 C CH3COOH D CHF3
D
Which of these substances has permanent dipole-dipole attractions between molecules? A CCl4 B C2F4 C (CH3)2CO D CO2
C
What is the formula of calcium nitrate(V)?
Ca(NO3)2
Predict the type of crystal structure in solid zinc fluoride and explain why its melting point is high
Ionic
M2 = Theoretical moles Zn = 5.68 (= 0.0869) 65.4
M3 = M1 × 100 / M2 = (0.0784 × 100 / 0.0869) M4 = 90.2% OR 90.3%
If not ionic CE = 0/3
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(b)
Strong (electrostatic) attraction (between ions)
between oppositely charged ions / + and − ions / F− and Zn2+ ions
State the strongest type of intermolecular force in water and in hydrogen sulfide
Water …………………………………………………………………………………………….. Hydrogen sulfide …
H bonds
Van der waals
Sulfur(IV) oxide reacts with water to form a solution containing ions.
Write an equation for this reaction.
SO2 +H2O→H+ +HSO3-
Write an equation for the reaction between the acidic oxide, phosphorus(V) oxide, and the basic oxide, magnesium oxide.
P4O10 + 6MgO → 2Mg3(PO4)2
Group 2 metals and their compounds are used commercially in a variety of processes and applications.
(a)
(b)
(c)
State a use of magnesium hydroxide in medicine. ……………………………………………………………………………..
Eases digestion
Calcium carbonate is an insoluble solid that can be used in a reaction to lower the acidity of the water in a lake.
Explain why the rate of this reaction decreases when the temperature of the water in the lake falls.
(1)
………………………………………………………………………………………………………. ………………………….
M1 Decrease in T decreases the energy of the particles
M2 Decrease in the number of particles
E ≥ E Activation energy
M3 Fewer successful collisions
