2018 Flashcards Preview

Chemistry O.L. > 2018 > Flashcards

Flashcards in 2018 Deck (40)
Loading flashcards...
1
Q

What is the white solid in the test tube in the collection of ethene gas experiment?

A

aluminium oxide

2
Q

Describe the appearance of the gas collected in the ethene gas experiment

A

colourless

3
Q

Explain why the first few test‐tubes of gas collected are not then used in the ethene gas experiment

A

impure contains a mixture of air and ethene

4
Q

What is suck-back? (Ethene experiment)

A

water from trough glass gets sucked back up delivery tube

5
Q

Why is suck-back hazardous?

A

cold water could cause test-tube (apparatus, glass) to crack (shatter, explode) releasing flammable gas into flame

6
Q

What precaution should be taken to avoid suck‐back?

A

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)

7
Q

Identify a reagent used to test ethene for unsaturation.

A

bromine (Br2) solution (water) / acidified potassium permanganate (H+/KMnO4)

8
Q

What colour change is a positive result in this test using the reagent (bromine, acidified potassium permanganate you identified?

A

red (brown, orange, yellow) /purple (pink) // to colourless / decolourised (colour fades)

9
Q

A combustion test was carried out on another test‐tube of ethene. (i) How was the combustion test carried out?

A

unstopper and quickly insert lighting taper (splint, match) into test tube / bring lighting taper (splint, match) into contact with ethene

10
Q

A combustion test was carried out on another test‐tube of ethene. (ii) Describe the flame observed.

A

bright {yellow, luminous, fairly clean, slightly (not very) sooty (smoky)}

11
Q

(iii) Copy, complete and balance the following equation for the complete combustion of ethene in oxygen: C2H4 + 3O2  _______ + ________

A

C2H4 + 3O2 → 2CO2 + 2H2O

12
Q

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?

A

(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)

13
Q

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.

A

burette / B / pipette / C / name given for B or C in (a)

14
Q

The 0.05 M Na2CO3 solution is a standard solution. Explain the underlined term.

A

solution of exactly known concentration (molarity)

15
Q

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?

A

methyl orange

WHAT: yellow (orange) to // red (pink, peach)

16
Q

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.

A

graduated cylinder / graduated dropper / pipette / syringe / burette

17
Q

Describe the appearance of the MnO2 catalyst.

A

black (brown, dark) / solid (powder)

18
Q

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.

A

graduated cylinder / graduated dropper / pipette / syringe / burette

19
Q

Describe the appearance of the MnO2 catalyst.

A

black (brown, dark) / solid (powder)

20
Q

Why does the rate of this reaction slow down as the minutes go by? (Manganese dioxide experiment)

A

hydrogen peroxide (reactant, reagent) used up

21
Q

Give one difference between Mendeleev’s periodic table of the elements and the modern periodic table.

A

no noble gases / some elements undiscovered / fewer elements

22
Q

Give the symbol of a metallic element used as a catalyst in the catalytic converter of a car.

A

Rh / Pt / Pd [Allow names.]

23
Q

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.

A

X: hydrogen (H2) //
Y: oxygen (O2)

24
Q

Write a balanced equation for the reaction that occurs when hydrogen gas reacts with chlorine gas producing hydrogen chloride.

A

H2 + Cl2 → 2HCl / ½ H2 + ½ Cl2 → HCl

25
Q

Calculate the pH of 0.15 M sulfuric acid (H2SO4) correct to one decimal place.

A

0.5

pH = – log10 [H+] / pH = – log10 [H3O+] / pH = – log10 0.3 / 0.3 moles H+ pH = – log 0.3 = 0.5

26
Q

An equation for the combustion of methanol in oxygen is: 2CH3OH + 3O2 -> 2CO2 + 4H2O
ΔH = – 1451 kJ
Is this reaction exothermic or endothermic?
Give a reason for your answer.

A

IS: exothermic
GIVE: ΔH negative / methanol (CH3OH) is a fuel / combustion reactions exothermic (give out heat)

27
Q

The molecular formula of glucose is C6H12O6. Write the empirical formula for glucose.

A

CH2O

28
Q

What happens during the primary stage of sewage treatment?

A

settlement / settling / screening / sedimentation

29
Q

A 500 cm3 sample of swimming pool water contained 0.11 g of dissolved solids. Express this concentration in parts per million (p.p.m. or mg per litre).

A

220 ppm (mg l–1)

  1. 11 × 2 = 0.22 g per litre
  2. 22 × 1000 = 220 ppm (mg l–1)
30
Q

Identify the process defined as ‘emission of an electron by an unstable nucleus’.

A

beta-decay (beta-radiation) / β-decay (β-radiation)

31
Q

Name the soccer‐ball shaped molecule made up of 60 carbon atoms that was discovered in 1985.

A

buckminsterfullerene / bucky ball / fullerene

32
Q

Why are industrial reaction vessels often made of steel?

A

unreactive (inert, stable) / doesn’t corrode / can be pressurized / minimum maintenance

33
Q

Argon (Ar) is a gaseous unreactive element that exists as single atoms. Why is this element unreactive?

A

argon has eight electrons in outer shell / argon has a stable electron arrangement (configuration) / argon is a noble (inert) gas

34
Q

Define electronegativity

A

relative (measure of) attraction / number expressing (giving) attraction // for shared electrons (pair) / for electrons in a covalent bond (2 × 3)

35
Q

What boiling point is most likely to have ionic bonding?

A

high melting (boiling) point

36
Q

What boiling point is most likely to have pure covalent bonding?

A

low melting (boiling) point

37
Q

What boiling point is most likely to be gaseous and have polar covalent bonding?

A

boiling point (b.p.) below room temperature

38
Q

What is the shape of a water molecule?

A

v-shaped / v-planar / bent

39
Q

What general term is used for compounds, like those shown in the table, that contain only carbon and hydrogen atoms?

A

hydrocarbon(s)

40
Q

Name an aromatic compound and it’s molecular formula. Is it commonly used? Why?

A

benzene, C6H6, no because it is carcinogenic / toxic / harmful / poisonous / dangerous