(a) DCPIP is an indicator and can be used to determine the rate of respiration of organisms such
as yeast.
(i) State the category of indicators to which DCPIP belongs.
..................................................................................................................................... [1]
(ii) Describe the colour change that occurs in DCPIP during experiments to determine the
rate of respiration.
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(b) An investigation was carried out to determine the effect of temperature on the rate of
respiration of yeast.
• A suspension of yeast cells was added to a test‑tube containing glucose solution.
• A further four test‑tubes were set up in the same way.
• One test‑tube was placed in a water‑bath at 10 °C for 5 minutes.
• DCPIP was added to the test‑tube and the time taken for the DCPIP to change colour
was measured.
• The experiment was repeated using the other test‑tubes at 20° C, 30 °C, 40 °C and 50 °C.
The results are shown in Fig. 6.1.
(cid:44)(cid:1)(cid:1)(cid:1)(cid:1)(cid:9)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:7)(cid:44)
(c) LCA10 is a different form of LCA caused by a recessive mutation in the CEP290 gene.
This gene codes for the protein CEP290, which is involved in the correct functioning of
photoreceptor cells in the retina.
The mutation in CEP290 causes an error to be made when the primary transcript is spliced to
form messenger RNA (mRNA). The abnormal mRNA that is formed has an extra sequence of
RNA nucleotides, known as exon X, between exon 26 and exon 27. Exon X contains a STOP
codon.
Fig. 3.1 compares the effect of the mutation in CEP290 with the normal gene expression.
normal LCA10
exon intron exon section of DNA exon mutation exon
of CEP290
Question
Mathematics
Edexcel2024
100 mol dm−3 acid
hydrochloric acid HCl 1.00
sulfuric acid H SO 0.98
10 20 30 40 50 0 10 20 30 40 50
Volume of NaOH / cm3 Volume of NaOH / cm3
*P76895A0828*
DO
NOT
WRITE
IN
THIS
AREA
DO
NOT
WRITE
IN
THIS
AREA
DO
NOT
WRITE
IN
THIS
AREA
AERA
SIHT
NI
ETIRW
TON
OD
AERA
SIHT
NI
ETIRW
TON
OD
AERA
SIHT
NI
ETIRW
TON
OD
PMT
(c) Some information about acids in aqueous solution is given.
Comment on these pH values. No calculations are required.
(4)
pH of a solution of
Name of acid Formula of acid
of river water
• the Mn2+ ions reacted with the dissolved oxygen forming a precipitate of
manganese(IV) oxide hydroxide
2Mn2+(aq) + O (aq) + 4OH–(aq) → 2MnO(OH) (s)
Question
Mathematics
Edexcel2023
Compare and contrast the role of the catalysts in these reactions.
(6)
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Question
Mathematics
Edexcel2023
800 mol dm–3 of sodium hydroxide solution.
This resulted in a temperature rise of 2.9 °C.
Calculate the standard enthalpy change of neutralisation, Δ Hd, of
neut
quinic acid in kJ mol–1.
[Assume the density of both solutions is 1.0 g cm–3.
specific heat capacity of solution formed = 4.18 J g–1 °C–1]
(3)
Question
Mathematics
Edexcel2023
Na Mg Al Si P
Elements in Period 3
Explain the variations in melting temperature across the period in terms of the
structure and bonding in these elements.
(6)
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The potato plant, Solanum tuberosum, is an important food crop. Crop yield is reduced if the
leaves of the plant are eaten by the larvae (immature stages) of the Colorado beetle, Leptinotarsa
decemlineata.
Crop scientists used recombinant DNA technology to create two genetically modified (GM)
varieties of potato plant. These plants produce proteins that are poisonous to insects.
• GM potato variety A contains two new genes, SN and Bt.
• GM potato variety B contains two new genes, SN and OCII.
The new varieties were tested by having a constant number of Colorado beetle larvae introduced
to the plants at time 0 hours. The number of larvae that were alive after 24, 48 and 72 hours was
recorded. The percentage of the larvae that had died in each time interval was calculated. This
was repeated for potato plants that had not been genetically modified (non-GM).
Table 4.1 shows the percentage of Colorado beetle larvae that had died on the GM potato plant
varieties and on non-GM potato plants.
Table 4.1
percentage of Colorado beetle larvae that had died
type of potato plant
The potato plant, Solanum tuberosum, is an important food crop. Crop yield is reduced if the
leaves of the plant are eaten by the larvae (immature stages) of the Colorado beetle, Leptinotarsa
decemlineata.
Crop scientists used recombinant DNA technology to create two genetically modified (GM)
varieties of potato plant. These plants produce proteins that are poisonous to insects.
• GM potato variety A contains two new genes, SN and Bt.
• GM potato variety B contains two new genes, SN and OCII.
The new varieties were tested by having a constant number of Colorado beetle larvae introduced
to the plants at time 0 hours. The number of larvae that were alive after 24, 48 and 72 hours was
recorded. The percentage of the larvae that had died in each time interval was calculated. This
was repeated for potato plants that had not been genetically modified (non-GM).
Table 4.1 shows the percentage of Colorado beetle larvae that had died on the GM potato plant
varieties and on non-GM potato plants.
Table 4.1
percentage of Colorado beetle larvae that had died
type of potato plant
(1)
A octahedral
B square planar
C tetrahedral
D trigonal bipyramidal
(iii) The equilibrium position for the dissociation of molten I Cl lies to the left.
Question
Mathematics
Edexcel2023
The graph shows the melting temperatures of some elements in Period 3.
1800
1600
1400
1200
Melting
1000
temperature
/ K 800
600
400
200
2
Explain, in terms of electrons, why this is a redox reaction.
(2)
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(d) An experiment was carried out to determine the molar volume of hydrogen at
room temperature.
Question
Mathematics
Edexcel2022
This question is about the elements in Group 2 of the Periodic Table.
(a) Magnesium powder is added to a beaker of water containing a few drops of
Universal Indicator.
The apparatus is set up as shown and allowed to stand for a few days.
test tube filled with water
water and Universal Indicator
filter funnel
magnesium powder
State two changes that will be seen after a few days.
(2)
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(b) Explain how the trend in the reactivity of the Group 2 elements is determined by
their electronic configurations.
(3)
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