Groups 1 & 2 (Edexcel International A Level (IAL) Chemistry): Flashcards
Exam code: YCH11
1/640Still learning
Know0
What is the first ionisation energy of an element?
Was this flashcard helpful?
Cards in this collection (64)
What is the first ionisation energy of an element?
The first ionisation energy is the energy needed to remove the first outer electron from one mole of gaseous atoms of an element to form one mole of gaseous ions with a +1 charge.
What is the second ionisation energy of an element?
The second ionisation energy is the energy needed to remove the second outer electron from one mole of gaseous +1 ions of an element to form one mole of gaseous ions with a +2 charge.
Why does ionisation energy decrease going down Group 2?
Going down Group 2, the shielding effect increases and the distance between the outermost electrons and the nucleus increases. These factors outweigh the increased nuclear charge, so it becomes easier to remove the outer electrons.
How many electrons do Group 1 and Group 2 elements have in their outermost principal quantum shell?
Group 1 elements have one electron in their outermost principal quantum shell. Group 2 elements have two electrons in their outermost principal quantum shell.
True or False?
The increase in nuclear charge going down Group 2 is the main reason ionisation energy decreases.
False.
Although nuclear charge increases down the group, the increased shielding effect and greater distance of the outermost electrons from the nucleus outweigh this. These factors are why ionisation energy decreases.
Group 1 and Group 2 metals act as .......... agents by donating their outermost electrons to become .......... ions.
Group 1 and Group 2 metals act as reducing agents by donating their outermost electrons to become positive ions.
What charge do Group 1 metals typically form when they react to produce ions?
Group 1 metals form ions with a +1 charge. They lose their one outermost electron and are oxidised in the process.
What charge do Group 2 metals typically form when they react to produce ions?
Group 2 metals form ions with a +2 charge. They lose their two outermost electrons and are oxidised in the process.
Why does reactivity increase going down Group 1?
Going down Group 1, the outermost electron gets further from the nucleus. The force of attraction weakens, so less energy is needed to remove the outer electron. This makes the metal more reactive.
Why do alkali metals tarnish when exposed to air?
Alkali metals react with oxygen in the air to form a metal oxide. This dull oxide coating covers the surface of the metal. Metals lower in the group tarnish more rapidly.
Complete the general equation for Group 1 metals (M) reacting with chlorine:
2M (s) + Cl2 (g) → ..........
2M (s) + Cl2 (g) → 2MCl (s)
True or False?
The reactivity of Group 2 metals decreases going down the group.
False.
The reactivity of Group 2 metals increases going down the group. The outermost electrons get further from the nucleus, making them easier to lose.
What are the products when a Group 2 metal (M) reacts with cold water?
The products are the metal hydroxide, M(OH)2, and hydrogen gas, H2. The general equation is: M (s) + 2H2O (l) → M(OH)2 (aq) + H2 (g).
What products form when magnesium is heated in steam?
When magnesium is heated in steam, it reacts vigorously to form magnesium oxide (MgO) and hydrogen gas (H2). The equation is: Mg (s) + H2O (g) → MgO (s) + H2 (g).
Complete the general equation for Group 2 metals (M) reacting with oxygen:
2M (s) + O2 (g) → ..........
2M (s) + O2 (g) → 2MO (s)
Which Group 2 metals also form a peroxide when reacting with oxygen?
Strontium (Sr) and barium (Ba) also form a peroxide (MO2) as well as the standard oxide (MO) when reacting with oxygen.
How does the reaction of calcium with cold water compare to magnesium with cold water?
Calcium reacts fairly vigorously with cold water in an exothermic reaction. Magnesium reacts extremely slowly with cold water. This reflects the greater reactivity of calcium.
What product forms when a Group 2 metal reacts with chlorine gas?
The product is the metal chloride, MCl2. For example, magnesium reacts with chlorine gas to form magnesium chloride: Mg (s) + Cl2 (g) → MgCl2 (s).
What is limewater and how is it produced?
Limewater is a solution of calcium hydroxide, Ca(OH)2, in water. It is produced when calcium oxide (CaO) is added to water: CaO (s) + H2O (l) → Ca(OH)2 (s).
What products form when a metal oxide reacts with dilute hydrochloric acid?
A metal chloride and water are produced. The general equation is: metal oxide + dilute hydrochloric acid → metal chloride + water.
When Na2O reacts with water, the products are .......... and the solution formed is .......... .
When Na2O reacts with water, the products are NaOH (aq) and the solution formed is alkaline.
True or False?
BeO is a basic oxide, like all other Group 2 oxides.
False.
BeO is amphoteric — it can act as both an acid and a base. All other Group 2 oxides are basic.
What does amphoteric mean?
An amphoteric substance is one that can act both as an acid and as a base. For example, BeO is amphoteric as it can react with both acids and bases.
What observations are made when CaO reacts with water?
The reaction is vigorous and releases a lot of energy, causing some water to boil off. The solid appears to expand and open. The solution formed is alkaline (pH 11.0).
Why does MgO only form a weakly alkaline solution when added to water?
MgO is only slightly soluble in water, so relatively few hydroxide ions are released into solution. The resulting solution is weakly alkaline with a pH of around 10.0.
When a Group 2 metal hydroxide, M(OH)2, reacts with dilute HCl, the products are .......... and .......... .
When a Group 2 metal hydroxide, M(OH)2, reacts with dilute HCl, the products are a metal chloride and water.
What trend do Group 2 sulfates show in solubility going down the group?
Group 2 sulfates decrease in solubility going down the group. Magnesium sulfate is soluble, while barium sulfate is an insoluble white precipitate.
What is the trend in solubility of Group 2 hydroxides going down the group?
The solubility of Group 2 hydroxides increases going down the group. Mg(OH)2 is the least soluble and Ba(OH)2 is the most soluble.
What is the trend in solubility of Group 2 sulfates going down the group?
The solubility of Group 2 sulfates decreases going down the group. Magnesium sulfate is soluble while barium sulfate is essentially insoluble.
True or False?
The solubility of Group 2 sulfates increases going down the group.
False.
The solubility of Group 2 sulfates decreases going down the group. This is the opposite trend to Group 2 hydroxides.
As the solubility of Group 2 hydroxides increases going down the group, the concentration of .......... ions increases, making the solution more .......... .
As the solubility of Group 2 hydroxides increases going down the group, the concentration of OH– ions increases, making the solution more alkaline.
Why does the alkalinity of the solution increase going down Group 2 when metal oxides react with water?
The solubility of Group 2 hydroxides increases down the group. More hydroxide dissolves, releasing a higher concentration of OH– ions, which raises the pH and increases alkalinity.
Which Group 2 hydroxide has the lowest solubility in water?
Mg(OH)2 has the lowest solubility, approximately 2.0 x 10–5 mol per 100 g of water at 298 K.
How does the solubility of Group 1 hydroxides compare to Group 2 hydroxides?
Group 1 hydroxides are more soluble than Group 2 hydroxides. For example, KOH has a solubility of 121 g per 100 cm3 at 25 °C, while Ba(OH)2 is only 4.68 g per 100 cm3.
Group 1 compounds are all .......... in water, so they cannot be identified by precipitation reactions and instead require .......... to identify the cation.
Group 1 compounds are all soluble in water, so they cannot be identified by precipitation reactions and instead require flame tests to identify the cation.
What is thermal decomposition?
Thermal decomposition is the breakdown of a compound into two or more different substances when it is heated.
What are the products of the thermal decomposition of a Group 2 carbonate, XCO3?
The products are the metal oxide (XO) and carbon dioxide gas (CO2). The general equation is: XCO3 (s) → XO (s) + CO2 (g).
What are the products when a Group 2 nitrate is thermally decomposed?
The products are the metal oxide, oxygen gas (O2) and nitrogen dioxide gas (NO2). For example: Mg(NO3)2 → MgO + O2 + 2NO2.
True or False?
The thermal stability of Group 2 carbonates increases going down the group.
True.
Going down the group, more heat is needed to decompose the carbonates. Larger ions have lower polarising power, so the carbonate ion is less distorted and more thermally stable.
The only Group 1 carbonate that decomposes at Bunsen temperatures is .......... , producing .......... and CO2 (g).
The only Group 1 carbonate that decomposes at Bunsen temperatures is Li2CO3, producing Li2O and CO2 (g).
What products form when Group 1 nitrates (other than lithium nitrate) are thermally decomposed?
Group 1 nitrates from sodium to caesium decompose to give the metal nitrite (XNO2) and oxygen gas. The equation is: 2XNO3 (s) → 2XNO2 (s) + O2 (g).
What is the test for carbon dioxide gas?
Carbon dioxide gas turns limewater milky. This is due to the formation of a fine white precipitate of calcium carbonate: Ca(OH)2 (aq) + CO2 (g) → CaCO3 (s) + H2O (l).
What is the test for oxygen gas?
Oxygen gas relights a glowing splint. The oxygen supports combustion of the carbon in the splint, producing CO2.
Nitrogen dioxide is a .......... gas produced when Group 2 nitrates decompose, so these reactions should be carried out in a .......... .
Nitrogen dioxide is a brown-orange toxic gas produced when Group 2 nitrates decompose, so these reactions should be carried out in a fume cupboard.
Why does thermal stability of carbonates and nitrates increase going down Groups 1 and 2?
Larger ions lower in the group have lower polarising power. They distort the carbonate or nitrate ion less, so the bonds are stronger and more heat is needed to break them down.
What is a flame test?
A flame test is a qualitative technique used to identify metal ions by the characteristic colour they produce when heated strongly in a Bunsen flame.
What colours are produced in a flame test for lithium, sodium and potassium ions?
Lithium (Li+) — red
Sodium (Na+) — yellow
Potassium (K+) — lilac
What colours are produced in a flame test for calcium, strontium and barium ions?
Calcium (Ca2+) — brick-red
Strontium (Sr2+) — crimson
Barium (Ba2+) — green
True or False?
Magnesium produces a visible flame colour in a flame test.
False.
Mg2+ does not produce a visible flame colour. The energy emitted during the flame test involving magnesium is outside the visible spectrum.
The wire loop is cleaned in concentrated acid and held in the Bunsen flame before each flame test to avoid .......... from previous samples.
The wire loop is cleaned in concentrated acid and held in the Bunsen flame before each flame test to avoid contamination from previous samples.
Why does heating a metal ion in a flame produce a coloured emission?
Heat causes electrons to jump to a higher energy level. The electrons are unstable there and fall back to a lower level, releasing energy as visible light. The wavelength of this light determines the colour observed.
Why must only one type of metal ion be present when performing a flame test?
If two or more metal ions are present, their flame colours will mix, making identification unreliable. The test only works correctly when a single ion type is present.
The wire loop used in a flame test must be made of an .......... metal, such as .......... or platinum.
The wire loop used in a flame test must be made of an unreactive metal, such as nichrome or platinum.
True or False?
Sodium produces a lilac flame in a flame test.
False.
Sodium produces a yellow flame. A lilac flame is characteristic of potassium (K+).
How do you test a solution for the presence of ammonium ions (NH4+)?
Add sodium hydroxide solution to the sample and warm gently. Hold damp red litmus paper near the mouth of the test tube. If ammonium ions are present, ammonia gas is released, turning the red litmus paper blue.
What observation confirms the presence of ammonium ions in a solution?
Damp red litmus paper held near the test tube turns blue. This indicates the presence of ammonia gas, which is produced when NH4+ reacts with OH– from sodium hydroxide.
Complete the ionic equation for the reaction of ammonium ions with hydroxide ions:
NH4+ (aq) + OH– (aq) → .......... + H2O (l)
NH4+ (aq) + OH– (aq) → NH3 (g) + H2O (l)
How do you test a solution for the presence of carbonate ions (CO32–)?
Add dilute hydrochloric acid to the sample. Bubble the gas produced through limewater. Carbonate ions produce CO2 gas, which turns the limewater milky.
True or False?
The test for carbonate ions uses barium chloride solution to produce a precipitate.
False.
The test for carbonate ions uses dilute hydrochloric acid to produce CO2 gas, which is then bubbled through limewater. Barium chloride is used to test for sulfate ions.
How do you test a solution for the presence of sulfate ions (SO42–)?
Acidify the sample with dilute hydrochloric acid, then add a few drops of barium chloride solution. A white precipitate of barium sulfate (BaSO4) confirms the presence of sulfate ions.
When testing for sulfate ions, dilute HCl is added first in order to remove any .......... that could produce a precipitate and .......... with the results.
When testing for sulfate ions, dilute HCl is added first in order to remove any carbonates that could produce a precipitate and interfere with the results.
True or False?
A positive test for sulfate ions produces a white precipitate of barium sulfate.
True.
When barium chloride solution is added to a solution containing sulfate ions, an insoluble white precipitate of barium sulfate (BaSO4) forms. The ionic equation is: Ba2+ (aq) + SO42– (aq) → BaSO4 (s).
What is the ionic equation for the reaction of carbonate ions with hydrogen ions during the carbonate test?
2H+ (aq) + CO32– (aq) → CO2 (g) + H2O (l)
What alternative observation confirms ammonia gas is present during the ammonium ion test?
Ammonia gas produces white smoke when it comes into contact with fumes of hydrogen chloride (from concentrated HCl). The white smoke is ammonium chloride: NH3 (g) + HCl (g) → NH4Cl (s).
Sign up to unlock flashcards
or