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The names of the elements of Period 2 of the Periodic Table are shown.
lithium beryllium boron carbon nitrogen oxygen fluorine neon
Answer the following questions about these elements.
Each element may be used once, more than once or not at all.
Identify the element which:
(a) is a product of photosynthesis
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(b) has an oxide found in clean, dry air
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(c) forms a basic oxide with the formula $X_2O$
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(d) is a main component of fertilisers used to improve crop growth
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(e) has the highest rate of diffusion at room temperature
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(f) produces a red flame in a flame test
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(g) has only 5 electrons in each of its atoms
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(h) has an oxide responsible for acid rain.
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Potassium is a Group I element.
(a) Name and describe the bonding in potassium.
name ..................................................................................................................................................
description .....................................................................................................................................
...............................................................................................................................
.........................................................................................................................................................................
[4]
(b) Potassium combines with sulfur to form an ionic compound, potassium sulfide, $\text{K}_2\text{S}$.
(i) Give two physical properties of ionic compounds.
1 ..................................................................................................................................
2 ..................................................................................................................................
[2]
(ii) Complete the dot-and-cross diagram to show the electron arrangement and charges of the ions in potassium sulfide.
[3]
(c) When potassium is added to water, it reacts vigorously and a coloured flame is seen. The equation for the reaction is shown.
$$2\text{K}(s) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{KOH}(aq) + \text{H}_2(g)$$
(i) State the colour of the flame seen.
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(ii) The solution formed is potassium hydroxide, a strong alkali.
State the formula of the ion responsible for alkalinity in a solution.
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(iii) State the colour of litmus in a strong alkali.
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(iv) Calculate the volume, in $\text{cm}^3$, of hydrogen gas formed when 2.34 g of potassium is added to excess water at room temperature and pressure.
Use the following steps.
• Calculate the number of moles of potassium added.
= ............................... mol
• Determine the number of moles of hydrogen gas formed.
= ............................... mol
• Calculate the volume of hydrogen gas formed.
volume = ............................... $\text{cm}^3$
[3]
(d) Aqueous potassium hydroxide reacts with a dilute acid to produce aqueous potassium chloride, $\text{KCl}(aq)$, which is a salt.
(i) Name the dilute acid used.
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(ii) State the type of reaction taking place.
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(iii) Name the experimental technique used when salts are made by reacting a dilute acid with an aqueous alkali.
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(e) When aqueous silver nitrate, $\text{AgNO}_3(aq)$, is added to aqueous potassium chloride, a precipitate is formed.
(i) State the colour of the precipitate formed.
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(ii) Name the precipitate formed.
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(iii) Write the ionic equation for the reaction. Include state symbols.
................................................................................................................................................... [3]
542
506
592
Ammonia is made in an industrial process starting with nitrogen. The equation for the reaction is shown.
$$\text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3$$
(a) Name the industrial process used to make ammonia. [1]
(b) State the raw material from which nitrogen is obtained. [1]
(c) State what is meant by the symbol $\rightleftharpoons$. [1]
(d) State the temperature and pressure used in this industrial process.
temperature = \text{.....................} \text{°C}
pressure = \text{......................} \text{atm} [2]
(e) Name the catalyst used in this industrial process. [1]
(f) The forward reaction is exothermic.
State the effect, if any, on the position of the equilibrium when the following changes are made.
Explain your answers.
temperature is reduced
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pressure is reduced
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(g) Explain, in terms of particles, what happens to the rate of reaction when the temperature is reduced.
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.......................................................................................................................
....................................................................................................................... [3]
(h) Give the formula of the compound formed when sulfuric acid reacts with ammonia. [1]
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A student prepares calcium nitrate, $Ca(NO_3)_2,$ by adding calcium carbonate to dilute nitric acid.
(a) Write the chemical equation for this reaction. [2]
(b) Describe two observations during this reaction. [2]
(c) The student continues to add calcium carbonate until it is in excess. The student then removes the excess calcium carbonate by filtration and collects the aqueous calcium nitrate.
State the general term given to a solution collected from filtration. [1]
(d) The student gently heats the aqueous calcium nitrate until the solution is saturated.
(i) Suggest what is meant by the term saturated solution. [2]
(ii) Describe how crystals are produced from a hot saturated solution. [1]
(e) Calcium nitrate crystals are hydrated and have the formula $Ca(NO_3)_2·xH_2O$ where x is a whole number of molecules of water.
The student heats the crystals to remove the molecules of water.
$$\text{Ca(NO$_3$)$_2$} \cdot x\text{H$_2$O(s)} \rightarrow \text{Ca(NO$_3$)$_2$(s)} + x\text{H$_2$O(g)}$$
(i) State the term used to describe the calcium nitrate after the molecules of water have been removed. [1]
(ii) The student heats a sample of $Ca(NO_3)_2·xH_2O$ and forms 2.46 g of $Ca(NO_3)_2$ and 0.0600 moles of $H_2O$.
Determine the value of x. Use the following steps. [3]
- Calculate the $M_r$ of $Ca(NO_3)_2$.
- Determine the number of moles of $Ca(NO_3)_2$ formed.
- Determine the value of x in $Ca(NO_3)_2·xH_2O$.
(f) Nitrates decompose on heating.
Write the chemical equation for the reaction when solid sodium nitrate is heated. [2]
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Ethene is an alkene which reacts with bromine as shown in the equation.
$\text{C}_2\text{H}_4 + \text{Br}_2 \rightarrow \text{C}_2\text{H}_4\text{Br}_2$
(a) Write the general formula of alkenes.
.............................................................................................................................................................. [1]
(b) Describe the colour change seen when ethene is bubbled through aqueous bromine.
from .............................................................. to .............................................................. [1]
(c) In this reaction only one product is formed from two reactants.
Name this type of organic reaction.
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(d) Part of the energy profile diagram of this reaction is shown.
(i) The reaction is exothermic.
Complete the energy profile diagram for this reaction. Include:
• the position of the products
• an arrow to show the activation energy, labelled as A
• an arrow to show the energy change for the reaction.
[3]
(ii) The chemical equation for the reaction can be represented as shown.
Some bond energies are given.
[Table_1]
Use the bond energies in the table to calculate the energy change in this reaction.
Use the following steps.
• Calculate the energy needed to break bonds.
energy = ............................... kJ
• Calculate the energy released in making bonds.
energy = ............................... kJ
• Determine the energy change in this reaction.
energy change in this reaction = ............................... kJ/mol [3]
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542
Ester Y has the structure shown.
[Image_1: Structure of Ester Y]
(a) (i) Name ester Y.
....................................................................................................................................... [1]
(ii) Deduce the empirical formula of ester Y.
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(b) Complete the dot-and-cross diagram to show the arrangement of electrons in a molecule of ester Y.
[Image_2: Dot-and-cross diagram] [3]
(c) Ester Y can be made by reacting two organic compounds together.
Name the compounds and draw their structures.
Show all of the atoms and all of the bonds.
name ........................................................
structure
name ........................................................
structure [4]
(d) (i) Describe what is meant by the term structural isomer.
.......................................................................................................................................
....................................................................................................................................... [2]
(ii) Name a carboxylic acid which is a structural isomer of ester Y.
....................................................................................................................................... [1]
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566
