PL che

Question 1

Give the symbols of halogens. Write the valence electron configuration of halogens. How many valence electrons have a halogen?

Answer 1

7 valence electrons
F2: s^2p^5

Cl2: s^2p^5

Br2: s^2p^5

I2: s^2p^5

Question 2

List the halogens with names. Characterize the structure and chemical reactivity of elementary halogens.

Answer 2

Fluorine: pale green gas

Chlorine: yellowish green gas

Bromine: reddish brown liquid

Iodine: grey (purple vapors) solid

They are highly reactive
-The reactivity increases bottom to top

Question 3

Give the equation for the formation of Lugol’s solution. What is the medical use of Lugol’s solution?

Answer 3

External disinfectant

Mixture of Kl and iodine: I2 + KI^-1 = KI3^-1

Question 4

Name the following compounds:

HgI2

KIO3

NaClO4

Ca5(PO4)3F

Answer 4

Mercury (2) Iodide

Potassium Iodate

Sodium perchlorate

Fluorapatite

Question 5

Give the formulas for the following substances:

potassium chlorate

silver(I) iodide

perchloric acid

sodium hypochlorite

sodium fluoride

hydrochloric acid.

Answer 5

KClO3

AgIO3

HClO4

NaClO

NaF

HCl

Question 6

Give the general formula for hydrogen halides and give the oxidation number of halogens in them. Compare their acid strength.

Answer 6

1. They have Hydrogen (H) and a halogen (F, Cl, Br or I)
2. They have a -1 charge
3. Increasing acidity from HF → HCl → HBr → HI

Question 7

Give a reaction equation for the formation of hypochlorous acid from chlorine. Establish the oxidation numbers in the reaction equation. What is the practical importance of hypochlorous acid?

Answer 7

• Cl2 + H2O ←→ HCl + HOCl
• Its sodium salt are indispensable disinfectants

Question 8

Give the equation for the reaction of chlorine and sodium hydroxide, name the product. What is the practical importance of the product?

Answer 8

Cl2 + 2NaOH ←→ NaCl + NaOCl + H2O

Question 9

Why isn’t it supposed to mix household bleach and hydrochloric acid? Give two reaction equations.

Answer 9

• NaOCl + HCl → NaCl + HOCl
• Hocl is a weak acid that is isolated from the salts

1. HCl + HOCl ←→ Cl2+ H2O
2. HCl is a strong acid and it can cause eq to shift to right and Cl2 gas would be generated

Question 10

Give the electron configuration of the outer shell of oxygen. Characterize its electronegativity. Which are the usual oxidation numbers of oxygen in its compounds?

Answer 10

• Electron config: 2s^2 2p^4
• Very high electronegativity (2nd highest)
• Oxidation: -2 in compounds, -1 in peroxide, -.5 in superoxide

Question 11

Give the equation of ozone formation. What triggers the reaction in the atmosphere?

Answer 11

• O2 + O →O3
• Hydrogens generated from dioxygen by uv radiation of the sun triggers the reaction in the atmosphere

Question 12

What are oxygen gas and hydrogen peroxide used for in medical practice?

Answer 12

Hydrogen peroxide is used as a disinfectant against bacteria that are killed by liberated oxygen gas

Question 13

Give the equation for the spontaneous decomposition of hydrogen peroxide.

Answer 13

2H2O2 → 2H2O + O2

Question 14

Characterize the redox properties of hydrogen peroxide. What is the oxidation number of oxygen in this compound?

Answer 14

• 2H2O2 → 2(1) + 2(x) x=1
• Oxidation number of oxygen = -1
• Hydrogen can reduce to water since it is a non-stable oxidation state where it can either oxidize or reduce

Question 15

Describe the composition of ‘Hyperol’ and its use in medical practice.

Answer 15

• H2O2 and Urea will form a stable commercial available solid (Hyperol)
• Used as an disinfectant

Question 16

Name the family of compounds and the marked functional group in the figure below. Which is the strongest intermolecular force between the molecules of this family?

Answer 16

• Hydroxyl group
• Hydrogen bond is the strongest intermolecular force

Question 17

Write formulas for the following compounds and determine the oxidation numbers of sulfur in each case:

magnesium sulfate

sodium sulphite

iron(II) sulfide.

Answer 17

• magnesium sulfate: Mg(SO4)
  mg = +2, S = +6, O = -2
• sodium sulphite: Na2SO3
  Na = +1, S = +4, O = -2
• iron(II) sulfide: FeS
  Fe = +2 and S = -2

Question 18

Write the equation that describes the laboratory preparation of hydrogen sulfide.

Answer 18

FeS + 2H+ ← → H2S + Fe^+2

Question 19

Write equations for the formation of sulfurous acid and sulphuric acid from their anhydrides.

Answer 19

• H2O + SO2 ← → H2SO3
• H2SO3 + H2O ← → H2SO4 + 2H

Question 20

Disassociation of sulfuric acid in aqueous solution (2 equations)

Answer 20

H2SO4 —> H^+ + HSO4^-
HSO4^- <——> H^+ + SO4^2-

Question 21

Eq for neutralization of sulfuric acid reaction

Answer 21

H2SO4 + 2 KOH —> K2SO4 + 2H2O