Time to bond
Why do atoms form chemical bonds?
To achieve a full outer shell / stable electronic configuration
Name the ions present in acids and the ions present in alkalis.
Acids = H⁺ ; Alkalis = OH⁻
Define the term mole.
Amount of substance containing 6.02×10²³ particles
Name the first three alkanes.
Methane, ethane, propane
Name the element in Group 1 that reacts most vigorously with water.
Caesium or Francium (most violent)
Compare melting points of NaCl and CO₂. Explain the difference.
NaCl has high melting point due to strong ionic bonding; CO₂ is simple covalent with weak intermolecular forces → low melting point.
Describe how to prepare sodium chloride.
Add sodium hydroxide to hydrochloric acid.
Stir in warm acid until excess, filter, crystallise
How many moles in 18 g of water?
18 / 18 = 1 mol
Test to distinguish ethane vs ethene?
Bromine water → turns colourless with alkene
Draw and describe the energy profile of an exothermic reaction.
Reactants higher energy than products; downward energy change
Which of the following cannot conduct electricity? Why not?
A. Sodium chloride crystals (table salt)
B. Electrolyte containing calcium chloride solution
C. Pencil lead
D. Lead metal
A. Sodium chloride crystals (table salt)
Ionic compounds can only conduct electricity when aqueous or molten (flow of charge required)
How do you obtain pure dry crystals of sodium sulfate from sulfuric acid and sodium hydroxide?
Titration → evaporate until crystallisation → cool → filter → dry
Calculate the number of oxygen atoms in 0.25 mols of carbon dioxide.
0.25 × 2 x 6.02×10²³ = 3.01×10²³ atoms
What catalyst and temperature is used to crack long-chain alkanes?
Silica/Aluminium at 600-700 degrees celcius
State one use of cryolite in aluminium extraction.
Lowers the melting point of aluminium oxide
Calculate the percentage by mass of oxygen in CO₂.
2×16 / 44 ×100 = 72.7%
25.0 cm³ of 0.50 mol/dm³ HCl is titrated with NaOH. What volume of 0.25 mol/dm³ NaOH is needed for neutralisation?
Moles HCl = 0.0125 → need 0.0125 mol NaOH → V = 0.0125 / 0.25 = 50 cm³/0.05dm3
A compound contains 40% C, 6.7% H, 53.3% O. Find its empirical formula.
CH₂O
Draw out the product formed when propanol is oxidised and name the oxidizing agent used.
Propanoic acid drawn, acidified potassium manganate
What is formed at the anode in the electrolysis of aqueous sodium chloride (brine)?
Write out the ionic equation.
Chlorine gas.
2Cl- --> Cl2 + 2e-
Explain the bonding + structure type in SiO₂ in detail including properties.
Giant covalent network.
Each Si bonded to 4 Os, each O bonded to 2 Si.
→ strong bonds throughout → high mp/bp, hard, insoluble, non-conductive.
I would like to make calcium sulfate. Explain how I can obtain pure crystals of this salt.
Calcium sulfate = insoluble so precipitation reaction
Calcium hydroxide/nitrate + sulfuric acid.
Filter, wash, dry.
4.0 g of hydrogen reacts with excess oxygen. What volume of water vapour forms at RTP?
Balanced equation: 2H2 + O2 --> 2H2O
Moles H₂ =4/2=2 mol → H₂O=2 mol → 48 dm³
Write the full reaction equation for methane and chlorine in UV light. What type of reaction requires UV light?
CH₄ + Cl₂ → CH₃Cl + HCl.
Photochemical
Predict the products at each electrode when aqueous copper(II) sulfate is electrolysed using inert electrodes.
Write out the ionic equations
Cathode → Cu(s);
Cu2+ + 2e- --> Cu
Anode → O₂ + H⁺ ions produced.
4OH- --> 2H2O + O2 + 4e-