Chemical reactions Flashcards
(3) Write the balanced equation for water decomposing to form hydrogen and
oxygen.
2H2O → 2H2 + O2 • reactant formula (1) • product formulae (1) • balancing correct formulae (1)
(2) Describe the test to show that a gas is hydrogen.
lighted splint
gas burns( 1)
• with (squeaky) pop (if air
present) (1)
(2) Describe the test to show that a gas is oxygen.
glowing splint (1) • relights (1)
(1) Seawater can also be decomposed using electrolysis.
Seawater is sodium chloride solution.
When this is decomposed one product is a toxic gas.
The toxic gas produced is
chlorine
(1) Give a safety precaution that should be taken when collecting this toxic gas.
use a fume cupboard/open all the
windows /(good) ventilation/wear a
gas mask
(1) When dilute hydrochloric acid reacts with copper oxide one of the products is
copper chloride
(2) Explain what is meant by electrolysis.
decomposition /break
down of {compound /
substance / electrolyte}(1)
• using electricity / electrical
energy / d.c supply (1)(3) Chlorine gas reacts with sodium hydroxide solution to form sodium chlorate(I), NaOCl, sodium chloride and water
Write the balanced equation for this reaction
reactant formulae (1)
• product formulae (1)
• balancing correct formulae
(1)
(1) Sodium chloride solution can be prepared by reacting sodium hydroxide solution
with an acid.
Give the name of the acid that must be used.
hydrochloric (acid)
(1) Which row of the table correctly identifies chalk, marble and limestone as
sedimentary or metamorphic rocks?
sedimentary / metamorphic /
sedimentary
(2) Suggest how you could show that, when calcium carbonate is heated, a
reaction takes place.
{find mass of / weigh} solid before
heating (1)
• (heat in a suitable container) and
{find mass / weigh} again (when
cool) (1)(2) Describe what you would observe when water is added, one drop at a time, to
cold calcium oxide
fizzing / hissing (1) • steam (1) • swells (1) • solid crumbles (to a powder) (1) • becomes hot (1)
(2) Write the balanced equation for the reaction of calcium hydroxide with
carbon dioxide
Ca(OH)2 + CO2 → CaCO3 + H2O
(1) State the common name for calcium hydroxide solution.
limewater
(2) Explain why calcium carbonate removes acidic gases from emissions in power
station chimneys.
(calcium carbonate) reacts with
{acidic gases / sulphur dioxide} (1)
• (because) calcium carbonate is a
base (1)
• to form a salt / calcium sulfate (1)
• neutralisation (reaction) (1)(1) State a hazard associated with chlorine gas.
toxic / poisonous (gas)
(2) Describe a test that can be used to identify a sample of gas as chlorine.
(damp blue) litmus (paper)
(1)
• (turns red then) white /
bleaches (1)
(1) State a use of chlorine.
making {poly(chloroethene / PVC /
solvents / medicines / agrochemicals /
disinfectants}
bleach / sterilising water / killing
bacteria(2)sodium chloride solution is electrolysed.
………….. NaCl + ………….. H2
O ……………………………… + ……………………………… + ………………………………
2NaCl + 2H2O → 2NaOH + H2
+ Cl2
(6) Use these results of electrolysis to compare the volumes of hydrogen and oxygen
formed and to show the effect of changing the time and the current on the
volumes of these gases.
Comparing volumes of hydrogen and oxygen
• (in each experiment) volume of hydrogen is twice volume of
oxygen
• because water molecules contain twice as many hydrogen
atoms as oxygen atoms / is H2O
• overall 2H2O → 2H2 + O2
Relating volumes of gases to current and time
• (from experiments 1 and 2) time doubles
• (from experiments 1 and 2) volumes of gases double
• Volumes of gases are directly proportional to the time for
electrolysis / passage of current
• (from experiments 1 and 3) as current x 1.5
• (from experiments 1 and 3) volumes of gases x 1.5
• volumes of gases are directly proportional to the current
(1) Sodium chloride solution can be prepared by reacting sodium hydroxide solution
with an acid.
Give the name of the acid that must be used.
hydrochloric (acid)
(1) State the form of energy used to carry out the electrolysis
electrical (energy) / electricity /
direct (electric) current
(1) Name the gas formed at the other electrode.
hydrogen
(2) Describe the test to show that a gas is chlorine.
(damp blue or red) litmus (paper)
((turns red and) bleached / white
(1) Which of these can be used to obtain chlorine from sea water?
electrolysis
(1) acid + metal carbonate salt + water + ………………………………………………………………………………
carbon dioxide
(2) CuO + ………….. HCl CuCl2= + ……………………….
CuO + 2 HCl → CuCl2 + H2O
(1) An acid reacts with a metal oxide to form
a salt and water only
(2) State two things you would see when solid copper carbonate reacts with
dilute nitric acid.
(acid) colourless (liquid/solution) (1) • (carbonate) green (solid) (1) • disappears (1) • effervesces/fizzes/bubbles (1) • blue (solution) (forms) (1)
(3) Write the balanced equation for the reaction of copper carbonate with dilute nitric acid
CuCO3 + 2HNO3 → Cu(NO3)2 + H20 + CO2
(2) Explain what is meant by electrolysis
decomposition (of compound/substance) (1) M1 • (by) (direct electric) current (1) M2
(2) Describe a test to show the gas is oxygen.
glowing splint (1) M1 • relights (1) M2
(2) Explain what is meant by electrolysis
decomposition (of
compound/substance
/electrolyte)(1)
• using (direct) current (1)
(2) Describe the test to show that a gas is chlorine.
(damp blue) litmus (paper)
(1)
• (turns red then) {bleaches
/ goes white} (1)
(1) C6H9Cl3
State the name of the polymer
poly(chloroethene)
(1) The reaction produces silver chloride as a precipitate.
In an equation this would be shown as
AgCl(s)
(1) The total mass of this apparatus was measured.
The flask was shaken to allow the silver nitrate solution and dilute
hydrochloric acid to react.
After the reaction the total mass of the apparatus was measured again.
State how the total mass of the apparatus after the reaction will compare with
the total mass of the apparatus before the reaction.
same/no change
(2) Write the balanced equation for the reaction of silver nitrate solution, AgNO3
,
with dilute hydrochloric acid to form silver chloride, AgCl, and nitric acid.
HCl + AgNO3 → AgCl + HNO3
(1) Dilute sulfuric acid was added to magnesium oxide.
State the name of the salt formed.
magnesium sulphate
