Topic 2 - Ionic Compounds and Analysis

Question 1

What is ionic bonding?

Answer 1

When atoms transfer (lose or gain) electrons to form charged (+vley or -vely) atoms (/group of atoms) called ions. As opposite charges attract, the ions are strongly attracted to one another

Question 2

Why do atoms transfer electrons?

Answer 2

To try to get a full outer shell

Question 3

How do sodium and chlorine bond together?

Answer 3

• Sodium atom gives outer electrons to chlorine (Na+, Cl-)

- Opposite charges attract so attracted together as ionic bond

Question 4

What Groups’ atoms most readily form ions?

Answer 4

1, 2, 6, 7

Question 5

How do Group 1 + 2 elements form ions?

Answer 5

• Lose electrons
• Positively charged ions
• Cations

Question 6

How do Group 6 + 7 elements form ions?

Answer 6

• Gain electrons
• Negatively charged ion
• Anions

Question 7

What charge do anions have?

Answer 7

Negative

Question 8

What charge do cations have?

Answer 8

Positive

Question 9

On the periodic table, where do two elements have to be to form ionic bonds with one another?

Answer 9

On opposite ends of the periodic table

Question 10

How does magnesium and oxygen form an ionic bond?

Answer 10

• Magnesium gives 2 outer electrons (Mg2+)
• Oxygen takes electrons (O2-) (oxide ion)
• Forms MgO, magnesium oxide

Question 11

How does sodium and oxygen form an ionic bond?

Answer 11

• 2 sodium give outer electron (2xna2+)
• Oxygen takes 2 electrons (O2-)
• Na2O

Question 12

How does calcium and chlorine form an ionic bond?

Answer 12

• Calcium transfers 2 outer electrons (1 to each chlorine: Ca2+, 2x Cl-)
• CaCl2

Question 13

What kind of structures do ionic compounds have?

Answer 13

Regular lattice

Question 14

How does an ionic regular lattice form?

Answer 14

• Ions form closely packed regular lattice arrangement
• Due to ionic bonds having strong electrostatic forces of attraction between oppositely charged ions
• Ionic compounds all have similar properties because of their structrue

Question 15

What are the properties of an ionic compound?

Answer 15

• High melting point
• High boiling point
• Conduct electricity when aqueous or molten

Question 16

Why do ionic compounds have high melting points and high boiling points?

Answer 16

• Due to the very strong bonds between the ions

- Takes a lot of energy to break these bonds

Question 17

Why do ionic compounds conduct electricity when aqueous or molten?

Answer 17

• Ions are separate + free to move so carry electric current

- Ions are held rigid in solid so aren’t free to move so can’t conduct electricity

Question 18

What are the two rules when naming a compound?

Answer 18

• When 2 different elements combine compound’s name is ‘something -IDE’
• When 3 or more different elements combine + 1 is oxygen, compound’s name is ‘something -ATE’

Question 19

What is the solubility rule for common salts of sodium, potassium and ammonium?

Answer 19

Soluble (-carbonates, hydroxides)

Question 20

Which salts of sodium, potassium and ammonium are insoluble?

Answer 20

Carbonates and hydroxides

Question 21

What is the solubility rule for all nitrates?

Answer 21

Soluble

Question 22

What is the solubility rule for common chlorides?

Answer 22

Soluble (-silver, lead)

Question 23

Which chloride salts are insoluble?

Answer 23

Silver chloride + lead chloride

Question 24

What is the solubility rule for common sulfates?

Answer 24

Soluble (-lead, barium, ammonium)

Question 25

Which sulfate salts are insoluble?

Answer 25

Lead sulfate, barium sulfate + calcium chloride

Question 26

What is the solubility rule for common carbonates and hydroxides?

Answer 26

Insoluble (-sodium, potassium, ammonium)

Question 27

How do you make a pure, dry sample of an insoluble salt by a precipitate reaction?

Answer 27

-Precipitation reaction: pick 2 soluble salts + react together -E.g. lead chloride: lead nitrate + sodium chloride (both soluble) Method: 1) - 1 spatula Pb(NO3)2 to test tube + fill w/ distilled water. Shake thoroughly so all dissolves. Same w/ NaCl (dist. water ensures no other ions) -Tip 2 solution into small beaker, stir so all mixes. PbCl should precipitate out 2) - Put filter paper into filter funnel, into conical flask -Pour contents through -Swill out beaker w/ dist. water, tip into beaker (ensures all product from beaker) 3) - Rinse all contents of filter paper w/ dist. water so all soluble sodium nitrate is washed away -Scrape lead chloride onto fresh filter paper + leave to dry

Question 28

How could you make a pure, dry sample of barium sulfate (BaSO4), an insoluble salt?

Answer 28

- Mix solution of barium 'something' + 'something' sulfate (as long as both soluble, e.g. barium nitrate + potassium sulfate) - Filter out precipitate of barium sulfate - Wash w/ dist. water (remove impurities) - Dry on filter paper

Question 29

How can barium sulfate be used for X-rays?

Answer 29

- Normally, only bones show in X-rays - Barium sulfate is opaque to X-rays; when drunk shows up gut so any problems i.e. blockages can be seen - Barium salts are toxic, but barium sulfate can be drunk safely as insoluble, so isn't absorbed into bloodstream, just passes though body - When patient drinks barium sulfate before X-ray, known as barium meal

Question 30

What colour flame do sodium ions (Na+) produce in the flame test?

Answer 30

Yellow/orange flame

Question 31

What colour flame do potassium ions (K+) produce in the flame test?

Answer 31

Lilac flame

Question 32

What colour flame do calcium ions (Ca2+) produce in the flame test?

Answer 32

Brick-red flame

Question 33

What colour flame do copper ions (Cu2+) produce in the flame test?

Answer 33

Blue-green flame

Question 34

How would you do a flame test in a lab?

Answer 34

- Dip clean wire loop into sample of compound + put into clear blue part of Bunsen flame (hottest part) - Make sure wire loop is really clean by dipping into HCl + rinsing with dist. water

Question 35

How do you test for carbonates (CO3 [2-])?

Answer 35

-React carbonate w/ dilute acid -Bubble gas produced through limewater, as if carbonate, CO2 released which turn limewater cloudy acid+carbonate-->salt+water+carbon dioxide

Question 36

How do you test for sulfate ions (SO4 [2-])?

Answer 36

-Add dilute HCl, followed by barium chloride, BaCl2 -White precipitate of barium sulfate means original compound was a sulfate Ba[2+](aq) + SO4 [2-] (aq) --> BaSO4 (s}

Question 37

How do you test for chloride ions (Cl-)?

Answer 37

-Add dilute nitric acid (HNO3), then silver nitrate solution (AgNO3) -Chloride give white precipitate of silver chloride Ag[+](aq) + Cl[-](aq) --> AgCl(s)

Question 38

How can spectroscopy be used to identify elements?

Answer 38

- Patterns of light emitted by elements in a heated sample are analysed - Each element present in sample produces different colours - Spectroscopy is fast + reliable + can be used to detect even small amounts of elements in a sample - Allowed scientists to discover new elements e.g. rubidium + caesium, both discovered as produced patterns of light not seen before