This question is about elements and compounds - AQA - GCSE Chemistry - Question 3 - 2017 - Paper 3
Question 3
This question is about elements and compounds.
3 (a) In 1869 Mendeleev produced an early version of the periodic table.
Figure 4 shows part of Mendeleev's periodic... show full transcript
Worked Solution & Example Answer:This question is about elements and compounds - AQA - GCSE Chemistry - Question 3 - 2017 - Paper 3
Step 1
Why did Mendeleev leave gaps in his periodic table?
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Answer
Mendeleev left gaps in his periodic table to accommodate for undiscovered elements, which he predicted would be found later. This arrangement allowed him to group elements with similar properties, ensuring that they fit the pattern of the periodic law.
Step 2
Give one reason why the elements Ti, V, Cr and Mn should not be where Mendeleev placed them.
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Answer
The placement of the elements Ti, V, Cr, and Mn was incorrect because they have different properties from the elements above them, which disrupts the pattern.
Step 3
Why, in terms of electrons, is bromine in Group 7?
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Bromine is in Group 7 because it has 7 electrons in its outer shell, which is the highest energy level, making it part of the halogens known for their reactivity.
Step 4
Explain why, in terms of electrons, bromine is more reactive than iodine.
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Bromine is more reactive than iodine because it has an outer shell that is closer to the nucleus, resulting in a stronger force of attraction between the nucleus and the outer electrons. Consequently, bromine can gain an electron more easily than iodine.
Step 5
Write the result for sodium iodide solution in Table 1.
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Yellow precipitate.
Step 6
Write the result for iron(II) chloride solution in Table 2.
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Green precipitate.
Step 7
Why would a flame test not show the presence of both sodium ions and potassium ions in the mixture?
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A flame test would not show the presence of both sodium ions and potassium ions because one color obscures the other, making it difficult to distinguish both colors.
Step 8
Complete Figure 7 to show the displayed structure of ethanoic acid.
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The displayed structure of ethanoic acid shows that it contains a carboxylic functional group, represented as -COOH, with the appropriate number of hydrogen atoms bonded to the carbon skeleton.
Step 9
Explain why ethanoic acid has a higher pH value than hydrochloric acid of the same concentration.
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Ethanoic acid is a weak acid, which means it is only partially ionized in solution, resulting in a lower concentration of hydrogen ions compared to hydrochloric acid, a strong acid, which fully dissociates. Therefore, ethanoic acid has a higher pH value.
