TUTORIAL #1 – ATOMS, MOLECULES AND IONS:

  1. Define ‘atomic number’ and ‘mass number’. Which of these can vary without changing the identity of the element?

Answer:

Atomic number is the number of proton in the nucleus of an atom.

Mass number is the total number of particles in the nucleus (proton plus neutron).

Mass number can vary without changing the identity of the element.

  1. Fill in the gaps in the following table, assuming each column represents a neutral atom:

Symbol / 52Cr / 55Mn / 112Cd / 222Rn / 207Pb
Protons / 24 / 25 / 48 / 86 / 82
Neutrons / 52-24 = 28 / 30 / 64 / 136 / 125
Electrons / 24 / 25 / 48 / 86 / 82
Mass number / 51.996 ≈ 52 / 54.938 ≈ 55 / 112.411 ≈ 112 / 222 / 207
  1. Write the correct symbol for the following:

a)The isotope of platinum that contains 118 neutrons;

b)The isotope of krypton with mass number 84;

c)The isotope of arsenic with mass number 75;

d)The isotope of magnesium that has equal number of protons and neutrons.

Answer: (a) (b) (c) (d)

  1. Name the following ionic compound:

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(a)MgO

(b)AlCl3

(c)Li3PO4

(d)Ba(ClO4)2

(e)Cu(NO3)2

(f)Fe(OH)2

(g)Ca(C2H3O2)2

(h)Cr2(CO3)3

(i)K2CrO4

(j)(NH4)2SO4

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Answers:

(a)Magnesium oxide

(b)Aluminium chloride

(c)Lithium phosphate

(d)Barium perchlorate

(e)Copper(II) nitrate

(f)Iron(II) hydroxide or ferum(II) hydroxide

(g)Calcium ethanoate or calcium acetate

(h)Chromium(III) carbonate

(i)Potassium chromate or kalium chromate

(j)Ammonium sulphate

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  1. Give the name or chemical formula, as appropriate, for the following acids:

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(a)HBrO3

(b)HBr

(c)H3PO4

(d)Hypochlorous acid

(e)Iodic acid

(f)Sulfurous acid

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Answer:

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(a)Bromic acid

(b)Hydrobromic acid

(c)Phosphoric acid

(d)HClO

(e)HIO3

(f)H2SO3

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  1. Give the name or chemical formula, as appropriate, for each of the following:

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(a)SF6

(b)IF5

(c)XeO3

(d)Dinitrogentetroxide

(e)Hydrogen cyanide

(f)Tetrafosforushexasulfide

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Answer:

(a) Sulfur hexafluoride

(b)Iodine pentafluoride

(c)Xenon trioxide

(d)N2O4

(e)HCN

(f)P4S6

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EXTRA QUESTIONS – DIMENSIONAL ANALYSIS (a.k.a. factor label method):

  1. The Tesla all-electric car is claimed to have a top speed of 130 miles/hour. What is this speed in km/hour?

Answer:

  1. A large sport utility vehicle moving at a speed of 125 km/hour might use gasoline at a rate of 16 Liters per 100km. what does this corresponds to in unit of mile per gallon?

Answer:

  1. A 20-cent coin has a mass of 5.67 g and is approximately 1.55 mm thick.

a)How many coins would have to be stacked to reach 575 feet?

Answer:

b)How much would this stack weigh (in kg)?

Answer:

c)How much money (in RM) would this stack contain?

Answer:

  1. The density of air at ordinary atmospheric pressure and 25oC is 1.19 g/L. What is the mass (in kg) of the air in a room that measures 12.5 ft  15.5 ft  8.0 ft?

Answer: 52 kg of air

Xtra-Xtra Qs:

  1. Which two of the following are isotopes of the same element: ; ; ? What is the identity of the element whose isotopes you have selected?

Answer: The isotopes are and and the element is sulfur, S

  1. Each of the following isotopes is used in medicine. Indicate the number of protons and neutrons in each isotope:

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(a)Phosphorus-32

(b)Chromium-51

(c)Cobalt-60

(d)Technetium -99

(e)Iodine-131

(f)Thallium-201

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Answer:

Isotope / # of proton / # of neutron
Phosphorus-32 / 15 / 32-15 = 17
Chromium-51 / 24 / 51-24 = 27
Cobalt-60 / 27 / 60-27 = 33
Technetium -99 / 43 / 99-43 = 56
Iodine-131 / 53 / 131-53 = 78
Thallium-201 / 81 / 201-81 = 120
  1. Predict the chemical formula for the ionic compound formed by

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a)Ca2+ and Br–

b)K+ and CO32–

c)Al3+ and CH3COO–

d)NH4+ and SO42–

e)Mg2+ and PO43–

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Answer: a) CaBr2 b) K2CO3 c) Al(CH3COO)3 d) (NH4)2SO4 e) Mg3(PO4)2

  1. Predict whether each of the following compound is molecular or ionic:

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a)B2H6

b)CH3OH

c)LiNO3

d)Sc2O3

e)CsBr

f)NOCl

g)NF3

h)Ag2SO4

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Answer:

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a)Molecular

b)Molecular

c)Ionic

d)Ionic

e)Ionic

f)Molecular

g)Molecular

h)Ionic

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  1. Name the following compounds:

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a)K2O

b)NaClO2

c)Sr(CN)2

d)Co(OH)2

e)Fe2(CO3)3

f)Cr(NO3)3

g)(NH4)2SO3

h)NaH2PO4

i)KMnO4

j)Ag2Cr2O7

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Answer:

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a)Potassium oxide

b)Sodium chlorite

c)Strontium cyanide

d)Cobalt(II) hydroxide

e)Iron(III) carbonate

f)Chromium(III) nitrate

g)Ammonium sulfite

h)Sodium dihydrogen phosphate

i)Potassium permanganate or potassium manganate(VII)

j)Silver dichromate

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  1. Solve the following using dimensional analysis:

a)Convert 16 weeks to seconds.

b)What is 1.09 g/mL in lbs/gal?

c)What is 4.22 g/cm3 in lbs/ft3?

Answer:

a)

b)

c)

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