CGP EXAM QUESTIONS: EL Flashcards

Question 1

Q

Hydrogen, deuterium and tritium are all isotopes of each other

Identify one similarity and one difference between these isotopes

Answer

A

Similarity: All have same number of protons and electrons
Difference: All have different numbers of neutrons therefore different mass numbers

Question 2

Q

Hydrogen, deuterium and tritium are all isotopes of each other

Deuterium can be written as ²H. Determine the number of protons, neutrons and electrons in a neutral deuterium atom.

Answer

A

1 proton
1 neutron
1 electron

Question 3

Q

Hydrogen, deuterium and tritium are all isotopes of each other

Write the nuclear symbol for tritium, given that is has two neutrons

Question 4

Q

Identify and explain the similarity between

Answer

A

³²S²^- has 16 + 2 = 18 electrons
⁴⁰Ar has 18 electrons as well

Question 5

Q

Identify and explain the similarity between

Answer

A

Same number of protons
Each has 16 protons (atomic number of S must always be the same)
Isotopes - because have same number of protons but different numbers of neutrons therefore different mass numbers

Question 6

Q

Identify and explain the similarity between

Answer

A

Same number of neutrons
Ar = 40 - 18 = 22 neutrons
Ca = 42 - 20 = 22 neutrons

Question 7

Q

Scientific theories are constantly being revised in the light of new evidence. New theories are accepted because they have been successfully tested by experiments or because they help to explain certain observations
Niels Bohr thought that the model of the atom proposed by Ernest Rutherford did not describe the electrons in an atom correctly.

Why did he think this and how was his model of the atom different from Rutherford’s?

Answer

A

Bohr knew that if an electron was freely orbiting the nucleus it would spiral into it, causing the atom to collapse
His model only allowed electrons to be in fixed shells and not between them

Question 8

Q

Scientific theories are constantly being revised in the light of new evidence. New theories are accepted because they have been successfully tested by experiments or because they help to explain certain observations
Niels Bohr thought that the model of the atom proposed by Ernest Rutherford did not describe the electrons in an atom correctly.

According to the Bohr model of the atom, what happens when electrons in an atom move from one shell to another?

Answer

A

When an electron moves from one shell to another electromagnetic radiation is emitted or absorbed

Question 9

Q

Scientific theories are constantly being revised in the light of new evidence. New theories are accepted because they have been successfully tested by experiments or because they help to explain certain observations
Niels Bohr thought that the model of the atom proposed by Ernest Rutherford did not describe the electrons in an atom correctly.

How did the Bohr model explain the lack of reactivity of the noble gases?

Answer

A

The shells of an atom can only hold fixed numbers of electrons.

Noble gases have full shells and so do not react
OR a full shell of electrons makes an atom stable; noble gases have full shells and do not react because they are stable

Question 10

Q

Copper exists in two main isotopic forms, ⁶³Cu and ⁶⁵Cu

Calculate the relative atomic mass of copper

(where is the mass spectrum)

Question 11

Q

Copper exists in two main isotopic forms, ⁶³Cu and ⁶⁵Cu

Explain why the relative atomic mass of copper may not be a whole number

Answer

A

A sample of copper is a mixture of 2 isotopes of different abundances. The average mass of these isotopes isn’t a whole number

Question 12

Q

The percentage make-up of naturally occuring sulfur is 0.752% of ³³S, 4.25% of ³⁴S and 0.0110% of ³⁶S, and the rest is ³²S.

What method is used to determine the mass and abundance of each isotope?

Answer

A

mass spectrometry

Question 13

Q

The percentage make-up of naturally occuring sulfur is 0.752% of ³³S, 4.25% of ³⁴S and 0.0110% of ³⁶S, and the rest is ³²S.

Use the information to determine the relative atomic mass of sulfur

Answer

A

% of ³²S = 100 - 0.752 - 4.25 - 0.0110 = 94.887

887 x 32 = 3039.584
752 x 33 = 24.816
25 x 34 = 144.5
0110 x 36 = 0.396

3039.584 + 24.816 + 144.5 + 0.396 = 3209.296
A_r of S = 3209.296/100 = 32.1
* divide by 100 because working with percentages

Question 14

Q

Calculate the mass of propene required to produce 49.2g of bromopropane:
C₃H₆ + HBr –> C₃H₇Br

Answer

A

M of C₃H₇Br = (3 x 12) + (7 x 1) + (1 x 79.9) = 122.9g

Number of moles of C₃H₇Br = 49.2/122.9 = 0.400 moles

From the equation, 1 mole of C₃H₇Br is made from 1 mole of C₃H₆ so, 0.400 moles C₃H₇Br is made from 0.400 moles C₃H₆

M of C₃H₆ = (3 x 12) + (6 x 1) = 42g
so the mass of 0.400 moles C₃H₆ = 0.400 x 42 = 16.8g

Question 15

Q

Balance the equation:

KI + Pb(NO₃)₂ –> PbI₂ + KNO₃

Answer

A

2KI + Pb(NO₃)₂ –> PbI₂ + 2KNO₃

Question 16

Q

Calcium carbonate (CaCO<sub>3</sub>) reacts with nitric acid (HNO<sub>3</sub>) in a neutralisation reaction. 
The products are carbon dioxide, water and a solution of calcium nitrate (Ca(NO<sub>3</sub>)<sub>2</sub>)

Write the balanced equation for this reaction

Answer

A

CaCO_3(s) + 2HNO_3(aq) –> Ca(NO₃)_2(aq) + CO_2(g) + H₂O_(l)

Question 17

Q

Calcium carbonate (CaCO<sub>3</sub>) reacts with nitric acid (HNO<sub>3</sub>) in a neutralisation reaction. 
The products are carbon dioxide, water and a solution of calcium nitrate (Ca(NO<sub>3</sub>)<sub>2</sub>)

Calculate the volume of 1.50 mol dm^-3 HNO³ needed to neutralise 1.84g of CaCO₃

Answer

A

M of CaCO₃ = 40.1 + 12 + (3 x 16) = 100.1 g mol^-1

Moles of CaCO₃ = 1.84/100.1 = 0.0184 moles

From equation : 1 mole of CaCO₃ neutralises 2 moles of HNO₃, so 0.0184 moles of CaCO₃ neutralises 0.0368 moles of HNO₃

Volume of HNO₃ = (number of moles/concentration) x 1000
= (0.0368/1.50) x 1000 = 24.5 cm³

Question 18

Q

Hydrocarbon X has a molecular mass of 78.0g mol^-1. It is found to have 92.3% carbon and 7.70% hydrogen by mass. Calculate the empirical and molecular formulae of X.

Answer

A

(Assume you have 100g of the compound)
No. of moles of C = 92.3/12 = 7.69 moles
No. of moles of H = 7.7/1 = 7.7 moles

Divide both by the smallest number - 7.69
So ration C : H = 1 : 1
So empirical formula = CH

Mass of atoms in the empirical formula = 12 + 1 = 13
No. of empirical units in molecule = 78/13 = 6
So molecular formula = C₆H₆

Question 19

Q

When 1.2g of magnesium ribbon is heated in air, it burns to form a white powder, which has a mass of 2g. What is the empirical formula of the powder?

Answer

A

Magnesium is burning, so its reacting with oxygen and the product is magnesium oxide
First work out the number of moles of each element

No. of moles Mg = 1.2/24 = 0.005 moles
Mass of O is everything that isn’t Mg = 2 - 1.2 = 0.8g
No. of moles O = 0.8/16 = 0.05 moles
Ratio Mg : O = 1 : 1
So empirical formula is MgO

Question 20

Q

When 19.8g of an organic acid, A, is burnt in excess oxygen, 33.0g of carbon dioxide and 10.8g of water are produced. Calculate the empirical formula for A and hence its molecular formula, if M_r (A) = 132.

Answer

A

First calculate the no. of moles of each product then the mass of C and H:

No. of moles of CO₂ = 33/44 = 0.75 moles
Mass of C = 0.75 x 12 = 9g
No. of moles of H₂O = 10.8/18 = 0.6 moles

0.6 moles H₂O = 1.2 moles H
Mass of H = 1.2 x 1 = 1.2g
Organic acids contain C, H and O, so the rest of the mass must be O
Mass of O = 19.8 - (9 + 1.2) = 9.6g
No. of moles of O = 9.6/16 = 0.6 moles

Moles ratio = C : H : O = 0.75 : 1.2 : 0.6
Divide by smallest
C : H : O = 1.25 : 2 : 1
carbon part of ration isn’t a whole number, so you have to multiply them all up until it is. As its fraction is 5/4 multiply all by 4.
So mole ration = C : H : O = 5 : 8 : 4
Empirical formula = C₅H₈O₄

Empirical mass = (12 x 5) + (1 x 8) + (16 x 4) = 132g
This is the same as what we’re told the molecular mass is, so the molecular formual is also C₅H₈O₄

Question 21

Q

42.9g of CuSO₄•xH₂O is heated until all the water has been driven off, leaving 27.3g of anhydrous copper sulfate. What is the value of x?

Answer

A

M of CuSO₄ = 63.5 + 32.1 + (4 x 16) = 159.6 g mol^-1

No. of moles of CuSO₄ = 27.3/159.6 = 0.171 moles

Mass of water = 42.9 - 27.3 = 15.6g
Moles of water = 15.6/18 = 0.867 moles
Divide by smallest:

Cu: 0.171/0.171 = 1
H₂O: 0.867/0.171 = 5.07
So the value of x is 5
(the formula is CuSO₄•5H₂O)

Question 22

Q

The equation below shows the reaction for the complete combustion of propene
C₃H₆ + O₂ –> CO₂ + H₂O

If the reaction of 91.3g of C₃H₆ produces an 81.3% yield, how many grams of CO₂ would be produce?

Answer

A

First need to balance equation:
2C₃H₆ + 9O₂ –> 6CO₂ + 6H₂O

M of C₃H₆ = (3 x 12) + (6 x 1) = 42g mol^-1
moles of C₃H₆ = 91.3/42 = 2.17 moles

From equation; 2 moles of C₃H₆ produce 6 moles of CO₂, so 2.17 moles of C₃H₆ produce (2.17/2) x 6 = 6.52 moles of CO₂

M of CO₂ = 12 + (2 x 16) = 44g mol^-1
So theoretical yield = 6.52 x 44 =287g
Actual yield = (percentage yield x theoretical yield)/100
Actual yield = (81.3 x 287)/100
= 233g

Question 23

Q

Calculate the volume of 1 mol dm^-3 hydrochloric acid solution needed to make 500cm³ of 0.5 mol dm^-3 hydrochloric acid solution

Answer

A

Volume = (0.5/1) x 500
= 250cm³

Question 24

Q

Describe how indicators are used and explain the importance of selecting an appropriate indicator when carrying out a titration. Include examples of indicators that would and would not be suitable for use in titrations.

Answer

A

5-6 marks: The answer explains how indicators are used and includes at least one suitable and one unsuitable indicator for acid/alkali titrations with reasoning. The answer has a clear and logical structure. The information given is relevant and detailed

3-4 marks: The answer explains how indicators are used and includes one example of a suitable or unsuitable indicator for acid/alkali titrations. The answer has some structure. Most of the information given is relevant and there is some detail included.

1-2 marks: The answer contains some explanation of how indicators are used but gives no examples of indicators for acid/alkali titrations. The answer has no clear structure. The information given is basic and lacking in detail. It may not all be relevant.

Points answer may include:
Indicators change colour when the solution reaches a particular pH to mark an endpoint. They are used in acid/alkali titrations to mark the end point of the reaction. Indicators used in titrations need to change colour quickly over a very small pH range. A few drops of indicator solution are added to analyte. The analyte/indicator solution can be placed on a white surface to make a colour change easy to see. Methyl orange and phenolphthalein are both good indicators for titrations as they quickly change colour when the solution turns from alkali to acid. Universal indicator is a poor indicator to use for titrations as its colour changes gradually over a wide pH range.

Question 25

Q

Calculate the concentration (in mol dm^-3) of a solution of ethanoic acid, CH₃COOH, if 25.4 cm³ of it is neutralised by 14.6 cm³ of 0.500 mol dm^-3 sodium hydroxide solution

CH₃COOH + NaOH –> CH₃COONa + H₂O

Answer

A

CH₃COOH + NaOH –> CH₃COONa + H₂O

No. of moles of NaOH = (0.500 x 14.6)/1000 = 0/00730 moles
From the equation, you know 1 mole of NaOH neutralises 1 mole of CH₃COOH, so if you’ve used 0.00730 moles NaOH you must have neutralised 0.00730 moles CH₃COOH

Concentration of CH₃COOH = (0.00730/25.4) x 1000 = 0.287 mol dm^-3

Question 26

Q

You are supplied with 0.750g of calcium carbonate and a solution of 0.250 mol dm^-3 sulfuric acid. What volume of acid will be needed to neutralise the calcium carbonate?

CaCO₃ + H₂SO₄ –> CaSO₄ + H₂O + CO₂

Answer

A

CaCO₃ + H₂SO₄ –> CaSO₄ + H₂O + CO₂

M of CaCO₃ = 40.1 + 12 + (3 x 16) = 100.1 g mol^-1
Number of moles of CaCO₃ = 0.750/100.1
= 7.49 x 10^-3 moles

From the equation, 1 mole CaCO₃ reacts with 1 mole H₂SO₄ so, 7.49 x 10^-3 moles of CaCO₃ reacts with 7.49 x 10^-3moles H₂SO₄

The volume needed is ((7.49 x 10^-3)/0.250)) x 1000
= 30.0 cm³

Question 27

Q

In a titration, 17.1 cm³ of 0.250 mol dm^-3 hydrochloric acid neutralises 25.0 cm³ calcium hydroxide solution

Write out a balanced equation for this reaction

Answer

A

Ca(OH)₂ + 2HCl –> CaCl₂ + 2H₂O

Question 28

Q

In a titration, 17.1 cm³ of 0.250 mol dm^-3 hydrochloric acid neutralises 25.0 cm³ calcium hydroxide solution

Work out the concentration of the calcium hydroxide solution

Answer

A

Ca(OH)₂ + 2HCl –> CaCl₂ + 2H₂O

Number of moles of HCl = (0.250 x 17.1)/1000
= 4.275 x 10^-3 moles

From equation , 2 moles HCl reacts with 1 mole Ca(OH)₂ so, 4.275 x 10^-3 moles HCl reacts with 2.1375 x 10^-3 moles Ca(OH)₂

So concentration of Ca(OH)₂ solution = ((2.1375 x 10^-3)/25.0) x 1000
= 0.0855 mol dm^-3

Question 29

Q

Potassium reacts with oxygen to form potassium oxide, K₂O

Give the electron configurations of the K atom and the K⁺ ion

Answer

A

K atom: 1s²2s²2p⁶3s²3p⁶4s¹ or [Ar] 4s¹
K⁺ ion: 1s²2s²2p⁶3s²3p⁶ or [Ar]

Question 30

Q

Potassium reacts with oxygen to form potassium oxide, K₂O

Give the electron configuration of the oxygen atom

Answer

A

1s²2s²2p⁴

Question 31

Q

What is the electron configuration of a manganese atom?

Answer

A

1s²2s²2p⁶3s²3p⁶3d⁵4s² or [Ar] 3d⁵4s²

Question 32

Q

Identify the element with the 4th shell configuration of 4s²4p²

Answer

A

Germanium

Question 33

Q

Suggest the identity of an atom, a positive ion and a negative ion with the configuration 1s²2s²2p⁶3s²3p⁶

Answer

A

Ar (atom)
K⁺ (positive ion)
Cl^- (negative ion)

Could have also suggested Ca²⁺ , S^2- or P^3- etc.

Question 34

Q

Give the electron configuration of the Fe⁺ ion

Answer

A

1s²2s²2p⁶3s²3p⁶3d⁶

Question 35

Q

Draw a labelled diagram to show the structure of sodium chloride. Include at least 12 ions

Answer

A

Diagram should include:
cubic structure with ions at corners
sodium ions and chloride ions labelled
alternating sodium ions and chloride ions

Question 36

Q

What is the name of the structure that sodium chloride has?

Answer

A

giant ionic (lattice)

Question 37

Q

Would you expect sodium chloride to have a high or a low melting point? Explain your answer.

Answer

A

You’d expect it to have a high melting point
Because there are strong bonds between the ions due to the electrostatic forces. A lot of energy is required to overcome these bonds

Question 38

Q

Ions can be formed by electron transfer

Explain this and give an example for a positive and a negative ion

Answer

A

Electrons move from one atom to another
Any correct examples of ions, one positive, one negative.
E.g. Na⁺ , Cl^-

Question 39

Q

Solid lead bromide does not conduct electricity, but molten lead bromide does. Explain this with reference to ionic bonding.

Answer

A

In a solid, ions are held in place by strong ionic bonds
When the solid is heated to melting point, the ions gain enough energy to overcome the forces of attraction and become mobile, so can carry charge (and hence electricity) through the substance

Question 40

Q

Which is the correct formula for aluminium chloride?

A) AlCl

B) Al₂Cl₃

C) Al₃Cl

D) AlCl₃

Answer

A

D

Aluminium is in Group 3, so it loses 3 electrons to become an aluminium ion Al³⁺
Chlorine is in Group 7, so it gains 1 electron to become chloride ion Cl^-
You need three chloride ions to balance the 3+ charge on the aluminium ion, so the formula of aluminium chloride is AlCl₃

Question 41

Q

Draw a dot-and-cross diagram (showing outer shell electrons only) to represent the bonding in the molecule silicon hydride (SiH₄)

Question 42

Q

Describe two physical properties that you would expect silicon hydride to exhibit.

Answer

A

E.g. Non-conductor of electricity (no free electrons)
Low melting point (simple molecular, non-polar molecule - like methane)

Question 43

Q

Methane melts at -183^oC. Magnesium oxide melts at 2800^oC
Explain this difference in terms of bonding

Answer

A

Methane is a simple molecular substance
When it melts only weak intermolecular forces are overcome
Magnesium oxide is ionic
so to melt it the strong electrostatic attractions must be broken, which requires more energy/higher temperatures

Question 44

Q

Draw a dot-and-cross diagram of the ammonia molecule (NH₃) showing the outer shell electrons only

Question 45

Q

Draw a dot-and-cross diagram of the hydrogen chloride molecule (HCl) showing the outer shell electrons only.

Question 46

Q

Ammonia reacts with hydrogen chloride to form ammonium chloride. Draw a dot-and-cross diagram to show the bonding in ammonium chloride.

Question 47

Q

Predict whether ammonium chloride is likely to be soluble or insoluble in water

Answer

A

Ammonium chloride is likely to be soluble in water. The polar water molecules can break apart an ionic lattice

Question 48

Q

Explain what is meant by metallic bonding. Draw a diagram to illustrate your explanation.

Answer

A

Metallic bonding results from the attraction between positive metal ions and a sea of delocalised electrons between them

Question 49

Q

Explain why calcium has a higher melting point than potassium

Answer

A

Calcium (Ca²⁺) has two delocalised electrons per atom, while potassium (K⁺) has only one delocalised electron per atom. So calcium has more delocalised electrons and therefore stronger metallic bonding.

Question 50

Q

Carbon dioxide is a covalent compound that sublimes (turns directly from a solid to a gas) at -78^oC. Silicon dioxide is a covalent compound that melts at 1610^oC.

Explain these differences in terms of bonding.

Answer

A

Carbon dioxide is a simple molecular substance
Covalent bonds between carbon and oxygen are strong but when carbon dioxide sublimes it is the weak intermolecular forces that are overcome.
Silicon dioxide has a giant covalent lattice structure, so to melt it the strong covalent bonds must be broken, which requires more energy/higher temperatures

Question 51

Q

Graphite is a giant covalent structure. However, unlike most giant covalent structures, it is able to conduct electricity. Explain why graphite is able to conduct electricity.

Answer

A

Graphite consists of sheets of carbon atoms, where each carbon atom is bonded to three others. This means that each atom has one free electron not involved in bonds, it is these free electrons that allow graphite to conduct electricity.

Question 52

Q

Electrical grade copper must be 99.9% pure. If sulfur and oxygen impurities react with the copper ions, its electrical conductivity is drastically reduced. Use your knowledge of metallic and ionic bonding to explain this.

Answer

A

Copper is metallically bonded and so delocalised electrons are free to move (carry electric current). Oxygen and sulfur form copper oxide/sulfide, fixing some electrons (as anions). This prevents them from moving and carrying charge.

Question 53

Q

Carborundum (silicon carbide) has the formula SiC and is almost as hard as diamond

What sort of structure would you expect carborundum to have as a solid?

Answer

A

Giant covalent

Question 54

Q

Carborundum (silicon carbide) has the formula SiC and is almost as hard as diamond

Apart from hardness, give two other physical properties you would expect carborundum to have.

Answer

A

Any 2 from:

high melting point
electrical non-conductor (insulator)
insoluble
good thermal conductor

Question 55

Q

Nitrogen and boron can form the chlorides NCl₃ and BCl₃

Draw the shape of NCl₃ and label it with the name of the shape and the approximate values of the bond angles.

Answer

A

shape: trigonal pyramidal
bond angle: 107^o

Question 56

Q

Nitrogen and boron can form the chlorides NCl₃ and BCl₃

Draw the shape of BCl₃ and label it with the name of the shape and the approximate values of the bond angles.

Answer

A

shape: trigonal planar
bond angle: 120^o exactly

Question 57

Q

Nitrogen and boron can form the chlorides NCl₃ and BCl₃

Explain why the shapes of NCl₃ and BCl₃ are different

Answer

A

BCl₃ has three electron pairs only around B
NCl₃ has four electron pairs around N, including one lone pair

Question 58

Q

The displayed formula of an organic compound is shown. Use electron pair repulsion theory to predict the shape and relevant bond angles of the bond around atoms A,B and C. Give reasons for your answers.

Answer

A

Atom A: shape: trigonal planar
bond angle: 120^o exactly
2 single bonds and 1 double bond

Atom B: shape: tetrahedral
bond angle: 109.5^o
4 bonding pairs

Atom C: shape; non-linear, bent
bond angle: 104.5^o
2 bonding pairs and 2 lone pairs

Question 59

Q

The graph shows first ionisation enthalpy plotted against atomic number. Which of the labelled points on the graph shows the first ionisation enthalpy of a Group 2 metal?

Question 60

Q

The graph shows first ionisation enthalpy plotted against atomic number. Which of the labelled points on the graph shows the first ionisation enthalpy of an element with a full outer electron shell?

Question 61

Q

The graph shows first ionisation enthalpy plotted against atomic number. Which of the labelled points on the graph shows the first ionisation enthalpy of an element in Period 3?

Question 62

Q

Explain why first ionisation energies show an overall tendency to increase across a period.

Answer

A

As you move across a period, the number of protons increases, meaning a stronger pull from the positively charged nucleus
making it harder to remove an electron from the outer shell
There are no extra inner electrons to add to the shielding effect

Question 63

Q

Explain why the melting point of magnesium is higher than that of sodium

Answer

A

Mg has more delocalised electrons per atom
and the ion has a greater charge density
This give Mg a stronger metal-metal bond, resulting in a higher melting point

Question 64

Q

State and explain the trend in the first ionisation enthalpy of Group 2 elements

Answer

A

First ionisation enthalpy decreases down Group 2
because the outer electrons are in shells further from the nucleus
The amount of shielding also increases because there are more filled inner shells
Both of these decrease the nuclear attraction for the outer shell electrons

Answer 56

A

Calcium (Ca²⁺)

Answer 57

A

CaCO₃_(s) –> CaO_(s) + CO₂_(g)

Answer 58

A

Barium carbonate is more thermally stable
This is because barium has a lower charge density than calcium, so it has weaker polarising power
The weaker polarising power of the barium ion causes less distortion of the carbonate ion (making it more thermally stable)

Answer 59

A

Mg(OH)₂ + 2HCl –> MgCl₂ + 2H₂O

Answer 60

A

CaO + H₂O –> Ca²⁺ + 2OH^-

or

CaO + H₂O –> Ca(OH)₂

Answer 61

A

Calcium hydroxide is more soluble in water than magnesium hydroxide, and so dissociation produces a higher concentration of hydroxide ions in solution

Answer 62

A

D) Cu(NO₃)₂

Answer 63

A

B) silver nitrate

Answer 64

A

Titrate some potassium hydroxide with a known volume of sulfuric acid and add some drops of indicator to show when the reaction’s finished
Then repeat titration using the same amount of acid and the exact amount of potassium hydroxide needed to neutralise it, so the salt isn’t contaminated with indicator
To get pure potassium sulfate, evaporate some of the water and then leave the rest to evaporate very slowly

Answer 65

A

Add dilute hydrochloric acid to the solution
and then test to see whether the gas giveon off is carbon dioxide by bubbling it through limewater
if limewater goes cloudy, the solution contains carbonates

Answer 66

A

Add a few drops of sodium hydroxide to a sample of the solution.
If a green precipitate forms, then iron(II) ions are present
Then add HCl followed by barium chloride solution to a sample of the solution. A white precipitate will form if sulfate ions are present.