2018 Flashcards
(40 cards)
What is the white solid in the test tube in the collection of ethene gas experiment?
aluminium oxide
Describe the appearance of the gas collected in the ethene gas experiment
colourless
Explain why the first few test‐tubes of gas collected are not then used in the ethene gas experiment
impure contains a mixture of air and ethene
What is suck-back? (Ethene experiment)
water from trough glass gets sucked back up delivery tube
Why is suck-back hazardous?
cold water could cause test-tube (apparatus, glass) to crack (shatter, explode) releasing flammable gas into flame
What precaution should be taken to avoid suck‐back?
break vacuum by removing end of delivery tube from water / break vacuum by loosening stopper / remove (reduce) heat from under test-tube only after letting air in (breaking vacuum)
Identify a reagent used to test ethene for unsaturation.
bromine (Br2) solution (water) / acidified potassium permanganate (H+/KMnO4)
What colour change is a positive result in this test using the reagent (bromine, acidified potassium permanganate you identified?
red (brown, orange, yellow) /purple (pink) // to colourless / decolourised (colour fades)
A combustion test was carried out on another test‐tube of ethene. (i) How was the combustion test carried out?
unstopper and quickly insert lighting taper (splint, match) into test tube / bring lighting taper (splint, match) into contact with ethene
A combustion test was carried out on another test‐tube of ethene. (ii) Describe the flame observed.
bright {yellow, luminous, fairly clean, slightly (not very) sooty (smoky)}
(iii) Copy, complete and balance the following equation for the complete combustion of ethene in oxygen: C2H4 + 3O2 _______ + ________
C2H4 + 3O2 → 2CO2 + 2H2O
A 0.05 M solution of sodium carbonate (Na2CO3) was prepared and then used to find the concentration of a hydrochloric acid (HCl) solution by titration.
Which piece of apparatus, A, B or C, was used:
(i) in making up the 0.05 M solution of Na2CO3,
(ii) to measure 25.0 cm3 of the Na2CO3 solution,
(iii) to measure the hydrochloric acid in each titration?
(i) A / volumetric flask / first / name given for A in (a)
(ii) C / pipette / third / name given for C in (a)
(iii) B / burette / second / name given for B in (a)
A 0.05 M solution of sodium carbonate (Na2CO3) was prepared and then used to find the concentration of a hydrochloric acid (HCl) solution by titration.
The wash bottle was used to rinse A, B, C and the conical flask with deionised water. Identify one of these pieces of apparatus that was rinsed again with a second liquid.
burette / B / pipette / C / name given for B or C in (a)
The 0.05 M Na2CO3 solution is a standard solution. Explain the underlined term.
solution of exactly known concentration (molarity)
A 0.05 M solution of sodium carbonate (Na2CO3) was prepared and then used to find the concentration of a hydrochloric acid (HCl) solution by titration.
(i) Name a suitable indicator for use in the titrations.
(ii) What colour change was observed at the end point?
methyl orange
WHAT: yellow (orange) to // red (pink, peach)
The student measured out 5 cm3 of hydrogen peroxide solution A, diluted it to 25 cm3 with deionised water and then transferred the diluted solution into a conical flask. Name a suitable piece of apparatus to measure out 5 cm3 of hydrogen peroxide solution A.
graduated cylinder / graduated dropper / pipette / syringe / burette
Describe the appearance of the MnO2 catalyst.
black (brown, dark) / solid (powder)
Manganese Dioxide Experiment: The student measured out 5 cm3 of hydrogen peroxide solution A, diluted it to 25 cm3 with deionised water and then transferred the diluted solution into a conical flask. Name a suitable piece of apparatus to measure out 5 cm3 of hydrogen peroxide solution A.
graduated cylinder / graduated dropper / pipette / syringe / burette
Describe the appearance of the MnO2 catalyst.
black (brown, dark) / solid (powder)
Why does the rate of this reaction slow down as the minutes go by? (Manganese dioxide experiment)
hydrogen peroxide (reactant, reagent) used up
Give one difference between Mendeleev’s periodic table of the elements and the modern periodic table.
no noble gases / some elements undiscovered / fewer elements
Give the symbol of a metallic element used as a catalyst in the catalytic converter of a car.
Rh / Pt / Pd [Allow names.]
The electrolysis of water, acidified with a few drops of sulfuric acid, was carried out in an apparatus like that shown. Inert (platinum) electrodes were used. Identify gas X and gas Y.
X: hydrogen (H2) //
Y: oxygen (O2)
Write a balanced equation for the reaction that occurs when hydrogen gas reacts with chlorine gas producing hydrogen chloride.
H2 + Cl2 → 2HCl / ½ H2 + ½ Cl2 → HCl
