Quiz 1

candidate name____________ class______

Total = 32

1. (3) Matter exists in three physical states, _____gas/gaseous_______, _____liquid_______, and ___solid_________.

2. (2) Two kinds of pure substances are _____element_______ and _____compound_______.

3. (9) Convert the following units (pay attention to the sig. fig.):

(1) 0.00 oC = ___273.15/273___ K = ___32/32.00___ oF [oF = 95(oC) + 32] 2’

(2) 1.0 ng = ___1.0 x 10^3___ pg = ___1.0 x 10^-6___ mg 2’

(3) To convert the density of water from g cm-3 to kg m-3, the conversion factor(s) we use are ___1 kg/1000 g___ and ___10^6 cm3/1 m3 or 1 cm3/10-6 m3___. 2’

(4) What is the mass in grams of 1.00 gal of water? The density of water is 1.00 g/mL. (show your working) (3’)

mL of water = 1.00 gal x 3.7854 L/1 gal x 1000 mL/1 L = 3.7854 x 10^3 mL 1’

grams = 1.00 g/mL x 3.7854 x 10^3 = 3.79 x 10^3 g 2’

(9)4. Fill in the blanks (the first pair is given) (9’)

symbols of elements C H O P Al

names of elements carbon hydrogen oxygen phosphorus aluminum

symbols of elements Hg Si Fe Pb Na

names of elements mercury silicon iron lead sodium

(4)5. Finish the following calculations

(1) 20.42 + 1.322 + 83.1 = ____104.8________ (2’, 1 for sig. fig.)

(2) 15.5 cm x 27.3 cm x 5.4 cm = ___2.3 x 10^3 cm3_________ (2’, 1 for sig. fig.) 1 point off for 2285.01 or 2285, allow the omission of the unit

6. Does the following diagram represent a chemical or physical change? How do you know? [Explain in full sentence(s)] (5’)

Key words: A chemical change 1’

Change of substances 1’, 2 substances originally 1’, 1 substance 1’

Must be in full sentences, 1 point for this requirement.

Quiz 2

Total = 37

1. (3’) Atoms are made of subatomic particles. And subatomic particles includes _______proton(s)_____, ___neutron(s)_________, ___electron(s)_________.

2. (2’) J. J. Thompson proved that _____electron_______ (one subatomic particle) comes out from the cathode in the cathode ray tube and it carries ____negative________ (positive, negative) charge.

3. (6’) Use your own words to depict the main features of the atomic models proposed by J. J. Thompson and Rutherford.

J. J. Thompson’s plum-pudding (3’):

positive charge  1’

is on a solid ball 1’ like a pudding,

electrons are embedded 1’

in this ball like plums on a pudding

Rutherford’s model (3’):

positive charge is on a nucleus (a core ...) 1’

most of the space is empty 1’

Electrons are circling (traveling) around the nucleus 1’

(6)4. An atom of rhodium (Rh) has a diameter of about 2.7 x 10-8 cm. Show your working.

(a) Convert its diameter to the unit of angstrom. (1 Ǻ = 10-10 m)

(b) If you assume that the Rh atom is a sphere, what is the volume in m3 of a single atom? (V = 4/3 πR3)

number of Ǻ = 2.7 x 10-8 cm x 1 m/100 cm x 1 Ǻ/10-10 m = 2.7 Ǻ

diameter in m = 2.7 Ǻ x 1 m/10^10 Ǻ = 2.7 x 10^-10 m

radius in m = 1.35 x 10^-10 m

V = 4/3 x 3.14 x (1.35 x 10-10)^3 m3 = 1.0 x 10-29 m3

5. (3’) Rubidium has two naturally occurring isotopes, Rubidium-85 (atomic mass = 84.9118 amu; abundance = 72.15%) and rubidium-87 (atomic mass = 86.9092 amu; abundance = 27.85%). Calculate the atomic weight of rubidium.

Ar = 84.9118 amu x 72.15% + 86.9092 x 27.85% = 85.47 amu

Give 1 point off for wrong sig. fig.

(7)6. Locate the following elements on the Periodic Table. (The first one is given.)

period group period group

Lithium 2 1 (or IA) Carbon 2 14 (or IVA)

Oxygen 2 16 (or VIA) Chlorine 3 17 (or VIIA)

Sodium 3 1 (or IA) Aluminum 3 13 (or IIIA)

Calcium 4 2 (or IIA) Phosphorus 3 15 (or VA)

(9)7. Name the following substances. (The first one is given.)

substance name substance name

NaCl sodium chloride HCl hydrochloric acid (also accept hydrogen chloride)

Mg(NO3)2 magnesium nitrate HClO hypochlorous acid (also accept hydrogen hypochlorite)

CaCO3 calcium carbonate HClO4 perchloric acid (also accept hydrogen perchlorate)

P2O5 diphosphorus pentoxide CH4 methane

N2O dinitrogen monoxide C3H8 propane

Quiz 3

total = 4 + 5 + 4 + 8 + 4 + 7 = 32

1. (4’) Define the following terms:

Combination reaction

It’s a reaction that two or more reactants produce only one product.

Decomposition reaction

It’s a reaction that only one reactant produces two or more products.

2. (5’) Balance the following equations:

Reminder: if the coefficient is 1, you should also write a “1” in the blanket, or you’ll lose the mark.

(1) ___2___Al(s) + ___3___Cl2(g) --> ___2___AlCl3(s)

(2) ___1___C7H8O2(l) + ____8__O2(g) --> ___7___CO2(g) + ___4___H2O(g)

(3) ___3___Mg(s) + ____1__N2(g) --> ___1___Mg3N2(s)

(4) ___1___C2H4(g) + ___3___O2(g) --> ____2__CO2(g) + ____2__H2O(g)

(5) ___1___PbCO3(s) --> ___1___PbO(s) + ___1___CO2(g)

3. (4’) Determine the formula mass of sucrose, C12H22O11. Calculate the percentage by mass of oxygen. Show your working. (Ar: C = 12.0, H = 1.0, O = 16.0)

FM = 12.0 x 12 + 1.0 x 22 + 16.0 x 11 = 342.0 1 pt off for 342

%O = 16.0 x 11 / 342.0 x 100% = 51.5% (also accept 51.46%)

4. (8’) Calculate the following quantities. Show your working:

(1) mass, in grams, of 1.50 x 10-2mol of CdS

(2) number of moles of NH4Cl in 86.6 g of this substance

(3) number of molecules in 8.447 x 10-2mol C6H6

(4) number of O atoms in 6.25 x 10-3mol Al(NO3)3

(1) mass = 1.50 x 10-2 mol x (112.4 + 32.1) g/mol = 2.17 g

(2) moles = 86.6 g x 1 mol/(14.0 + 4.0 + 35.5) g = 1.62 mol

(3) molecules = 8.447 x 10-2 mol x 6.02 x 1023 /mol = 5.09 x 1022

(4) O atoms = 6.25 x 10-3 mol x 6.02 x 1023 /mol x 9 = 3.39 x 1022

5. (4’) Determine the molecular formula of it.

Caffeine, a stimulant found in coffee, contains 49.5% C, 5.15% H, 28.9% N, and 16.5% O by mass and has a molar mass of 195 g/mol.

(Tip: deduce its empirical formula first, then molecular formula)

moles for C:H:O = 49.5/12.0 : 5.15/1.008 : 28.9/14.01 : 16.5/16.0 = 4.125 : 5.11 : 2.06 : 1.03 = 4:5:2:1

empirical formula is C4H5N2O

FM = 12.0 x 4 + 1.0 x 5 + 14.0 x 2 + 16.0 x 1 = 97.0

molecular formula is C8H10N4O2

6. (7’) One of the steps in the commercial process for converting ammonia to nitric acid is the conversion of NH3 to NO:

4 NH3(g) + 5 O2(g) --> 4 NO(g) + 6 H2O(g)

In a certain experiment, 2.00 g of NH3 reacts with 2.50 g of O2

(a) Which is the limiting reactant? (b) How many grams of NO and of H2O form? (c) How many grams of the excess reactant remain after the limiting reactant is completely consumed?

(a)

4 NH3 ~ 5 O2

17.0 x 4 ~ 32.0 x 5

68.0 ~ 160.0

2.00 g 2.50 g

O2 is not enough, so it’s limiting. 1’

(b)

5 O2 ~ 4 NO ~ 6 H2O

160.0 120.0 108.0

2.50 g x y

x = 2.50 g x 120.0/160.0 = 1.88 g 2’

y = 2.50 g x 108.0/160.0 = 1.69 g 2’

(c)

4 NH3 ~ 5 O2

68.0 ~ 160.0

z 2.50 g

z = 2.50 g x 68.0 / 160.0 = 1.06 g

grams remaining = 2.00 g – 1.06 g = 0.94 g 2’