24 questions. Try each one, then open the answer to check yourself and read the explanation.
Which of the following is an example of an Alcohol?
Answer: A (CH3OH)
CH3OH (methanol) contains the –OH group joined to an alkyl group, which makes it an alcohol (alkanol).
If element X forms the following compounds with fluorine: XF4, XF3, XF2. This illustrates the law of
Answer: B (multiple proportions)
The same two elements form several compounds in which the masses of fluorine joined to a fixed mass of X are in a simple ratio (4 : 3 : 2): the law of multiple proportions.
In the periodic table, the arrangements is in order of their
Answer: C (atomic numbers)
The modern periodic table arranges elements in order of increasing atomic number (number of protons).
How many grams of hydrogen gas will be produced when 6g of magnesium ribbon dissolves in 500cm3 of 6m HCl?
Answer: A (0.5g)
Mg + 2HCl → MgCl2 + H2. Mg = 6/24 = 0.25 mol and the acid (3 mol) is in excess, so 0.25 mol H2 = 0.25 × 2 = 0.5 g.
Which of the following options is correct?
Answer: D (metals form basic oxides, non-metals form acidic oxides)
As a general rule metal oxides are basic and non-metal oxides are acidic. A and B have exceptions (graphite conducts; sodium has low density).
The boiling point of methanol is lower than that of water because
Answer: A (intermolecular forces in methanol are weaker than those in water)
Water forms more hydrogen bonds per molecule than methanol, so less energy is needed to separate methanol molecules and it boils at a lower temperature.
The process that takes place during electrolysis is
Answer: C (negative ions are discharged at the anode by losing sufficient electrons to become neutral)
Negative ions (anions) move to the positive anode, where they give up electrons (oxidation) and become neutral atoms or molecules.
Isomerism is found to occur in
Answer: C (C4H10)
C4H10 exists as butane and 2-methylpropane; ethene and propane have only one possible structure.
During the dissolution of sodium nitrate in water, the ΔH is positive, this means that
Answer: B (the reaction is endothermic)
A positive ΔH means heat is absorbed from the surroundings, i.e. the process is endothermic.
During the addition of 9.8kg of solid potassium chlorate (KClO3) into 40cm3 of water, it was heated to dissolve all the solid. As the solution cooled crystals of potassium chlorate started forming at 66°C. Calculate the solubility of potassium chlorate at 66°C.
Answer: D (2.0moles per dm3)
Taking the mass as 9.8 g: moles of KClO3 = 9.8/122.5 = 0.08 mol in 0.040 dm3, so solubility = 0.08/0.04 = 2.0 mol dm−3.
The solution that will give a white precipitate with Barium chloride solution and a green flame test is
Answer: C (CuSO4)
A white precipitate with BaCl2 (BaSO4) shows sulphate; a green (blue-green) flame shows copper. So the salt is CuSO4.
NaOH Pellets are
Answer: B (deliquescent)
Sodium hydroxide pellets absorb so much water from the air that they dissolve in it and form a solution, which is deliquescence.
Alkenes
Answer: D (contain only carbon and hydrogen)
Alkenes are hydrocarbons (general formula CnH2n), made only of carbon and hydrogen; higher alkenes are liquids or solids and they are insoluble in water.
In the esterification of ethanoic acid with ethanol conc. H2SO4 serves as
Answer: A (a catalyst)
Concentrated H2SO4 provides H+ ions that speed up the esterification without being used up, so it acts as a catalyst.
The substance that conducts electricity from the following is
Answer: A (graphite)
In graphite each carbon uses only three electrons in bonding; the fourth is delocalised and can move, so graphite conducts.
The only acidic salt from the following is
Answer: B (NaHSO4)
NaHSO4 still has a replaceable hydrogen from the acid, which makes it an acid salt; the others are normal salts.
An isotope X has atomic number of 17 and a mass number of 36. What is the number of neutrons and protons in the isotope X?
Answer: A (19 neutrons, 17 protons)
Protons = atomic number = 17; neutrons = mass number − atomic number = 36 − 17 = 19.
In the preparation of H2SO4(l) as shown in the chemical equation below
SO3(g) + H2O(l) → H2SO4(l)
Given the heats of formation for SO3(g), H2O(l) and H2SO4(l) as −395KJmol−1, −286KJmol−1 and −811KJmol−1 respectively. Calculate the enthalpy (H) change of the reaction.
Answer: D (−130KJ)
ΔH = ΔHf(products) − ΔHf(reactants) = −811 − (−395 − 286) = −811 + 681 = −130 kJ.
In the experiment below, ammonium chloride crystals deposit on the walls of the test tube is as a result of
Answer: B (sublimation)
Heated ammonium chloride turns straight to vapour and then back to solid on the cooler part of the tube without melting: sublimation.
The graph below illustrates which of the gas law?
Answer: C (Charles)
The graph shows volume increasing in direct proportion to kelvin temperature (a straight line through the origin), which is Charles' law.
Calculate the minimum volume of oxygen needed for the complete combustion of a mixture of 10cm3 of CO and 15cm3 of H2.
Answer: C (12.5cm3)
2CO + O2 → 2CO2 needs 5 cm3 O2 for 10 cm3 CO; 2H2 + O2 → 2H2O needs 7.5 cm3 for 15 cm3 H2. Total = 12.5 cm3.
In the above graph, the behaviour of an ideal gas is illustrated by which of the curves?
Answer: B (Y)
For an ideal gas PV = RT, so PV/RT stays equal to 1 at every pressure: the horizontal line Y.
Given a solution of pH 4.398, calculate it's H+ ions concentration in moles per dm3.
Answer: D (4.0×10−5)
[H+] = 10−pH = 10−4.398 = 100.602 × 10−5 = 4.0 × 10−5 mol dm−3.
An unlabelled reagent bottle containing a clean organic liquid when tested with litmus paper and heated with metallic sodium. It was neutral to litmus paper and produced a colourless gas with the sodium. The liquid must be an
Answer: B (alkanol)
Alkanols are neutral to litmus but react with sodium to give hydrogen gas (2ROH + 2Na → 2RONa + H2); alkanes and alkenes do not react with sodium.