Download 4 - Berkeley City College

Fall 2015
Chem 1A, Test Review #1
1.
Perform the following conversions:
(a) 1.60 yard to centimeters (cm); (1 yard = 36 inches (exactly); 1 inch = 2.54 cm (exactly))
(b) 25 miles per gallon (mpg) to km per liter (kmpL);
(1 mile = 1.609 km; 1 gallon = 3.7854 L)
(c) 145 lb to kilograms. (1 lb = 453.6 g)
(d) 115oF to degrees Celsius (oC) and to Kelvin, respectively.
(e) The masses of four different samples of sodium chloride were measures as follows:
22.5 g, 5.238 g, 5,182 mg, and 723.5 mg. What is the total mass of salt with correct significant
figures?
2.
Indicate whether each of the following is a physical or chemical process:
(a) Silver tarnishes;
(b) Butter turns rancid;
(c) Salt dissolves in water;
(d) The toast is burnt;
3.
(e) alcohol vaporizes;
(f) the lake is frozen;
(g) the wood is rotting;
(h) The sugar has re-crystallized.
Classify each of the following as an element, a compound, a homogeneous or heterogeneous mixture:
(a) A bag of jelly beans;
(b) A cup of pure cane sugar;
(c) A bucket of muddy river water;
(d) A glass of white wine;
(e) A gallon of methanol;
(f) A tank of gasoline;
(g) A block of pure graphite.
(h) A sac of saw dust.
4.
A cylindrical metal bar that is 5.50 cm long weighs 19.70 g. The bar displaces 7.3 mL of water when
completely submerged. Calculate the density the metal and the diameter of the bar?
5.
Complete the following table for isotopes of elements.
Name of
Element
Magnesium
Atomic
Number
Mass
Number
Number of
Protons
15
Number of
Neutrons
13
16
Number of
Electrons
10
Isotope
Symbol
15
63
29 Cu
108
47
46
207
82
Pb2+
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Fall 2015
Chem 1A, Test Review #1
6.
Tungsten exists in two naturally occurring isotopes with the following atomic masses and natural
abundance: 185W (184.953 u; 37.07%) and 187W (186.956 u; 62.93%). Calculate the weighted average
atomic mass of tungsten.
7.
An element E reacts with oxygen gas to form an oxide with the formula E2O3. If the mass percent of
oxygen in the oxide is 17.29%, calculate the atomic mass of E and identify the element.
8.
Name each of the following compounds:
9.
10.
(a) NH4NO3 : ________________________;
(g) PCl5:____________________________
(b) Na2CO3: _______________________;
(h) HBrO2:__________________________
(c) SiF4 :____________________________;
(i) Fe(OH)3:_________________________;
(d) K2HPO4:_________________________;
(j) K2Cr2O7 :_________________________
(e) NiSO4:___________________________;
(k) SF6 :______________________________
(f) CrCl36H2O: ______________________;
(l) HIO4 :_____________________________
Write the correct formula of each of the following compounds:
(a) Calcium hypochlorite: _____________;
(g) Ammonium sulfate:____________
(b) Sodium phosphate: ___________;
(h) Hydrosulfuric acid:______________
(c) Phosphoric acid: ____________;
(i) Copper(II) sulfate pentahydrate: __________
(d) Lead(II) acetate:_______________;
(j) Diboron trioxide:____________
(e) Carbon tetrachloride: __________;
(k) Potassium permanganate: __________
(f) Lithium carbonate: _____________;
(l) Barium hydroxide: __________
(a) A compound composed of 68.85% carbon, 4.95% hydrogen, and 26.20% oxygen, by mass, has a
molecular mass of 122 amu. determine the empirical formula and the molecular formula of the
compound.
(b) When a 2.451-g sample of a compound that is composed of carbon, hydrogen and oxygen, is
completely combusted, it produces 5.821 g of CO2 and 2.979 g of H2O. Determine the mass percent
composition of the compound. Calculate the empirical formula of the compound.
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Fall 2015
Chem 1A, Test Review #1
11.
Write a balanced equation for each reaction described below:
(a) Solid ammonium dichromate decomposes when heated to produce solid chromium(III) oxide,
nitrogen gas, and water vapor.
(b) Calcium metal reacts with water to produce aqueous calcium hydroxide and hydrogen gas.
12.
Balance the following chemical equations using the smallest integer coefficients.
(a) ___C4H10O(l) + ___O2(g)  ___CO2(g) + ___H2O(g);
(b) ___NH3(g) + ___O2(g)  ___NO(g) + ___H2O(g);
(c) ___Ca(NO3)2(aq) + ___Na3PO4(aq)  ___Ca3(PO4)2(s) + ___NaNO3(aq)
13.
The following equation represents the combustion of octane (C8H18):
2C8H18(l) + 25 O2(g)  16CO2(g) + 18H2O(g)
(a) How many grams of O2 gas are consumed during the combustion of 345 g of octane?
(b) How many grams of CO2 and H2O, respectively, are produced when 345 g of octane is completely
combusted?
14.
An ammonium phosphate fertilizer is prepared by the following reaction:
3NH3(g) + H3PO4(aq)  (NH4)3PO4(s)
(a) If a reaction uses 245 g H3PO4 and 115 g NH3, which is the limiting reagent?
(b) How many grams of ammonium phosphate, (NH4)3PO4, will be produced when the limiting
reactant is completely reacted and the reaction yield is 100%?
(c) How many grams of (NH4)3PO4 are produced if the yield is 91.5%?
(d) If 318 g of ammonium phosphate were produced, what is the percent yield?
(e) How many grams of the excess reactant will remain unreacted at the end of the reaction?
15.
Magnesium hydroxide, Mg(OH)2, decomposes when heated to form magnesium oxide and water
vapor according the following equation:
Mg(OH)2(s)  MgO(s) + H2O(g)
When a 5.00-g solid mixture that contains Mg(OH)2 and MgO is heated until all of the Mg(OH)2 in
the mixture is completely decomposed, the solid residue that remains is found to weigh 3.65 g.
(a) Calculate the mass and the number of moles of water vapor given off. (b) How many grams of
Mg(OH)2 was present in the original mixture? (c) Calculate the mass percent of Mg(OH)2 in the
mixture.
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Fall 2015
Chem 1A, Test Review #1
Answers:
(b) 11 KmpL
(c) 65.8 kg
(d) 46.1oC; 319.3K
1.
(a) 146 cm
2.
(a) Chemical change
(e) Physical
3.
(a) Heterogeneous mixture
(d) Homogeneous mixture
(g) Element
4.
Density = 2.70 g/mL;
5.
Element
Atomic No.
Magnesium
12
Phosphorus
15
Copper
29
Silver
47
Lead
82
6.
Weighted average atomic mass of Tungsten = 186.21 amu
7.
Atomic mass of element E = 114.8 amu = Sb
8.
(a) Ammonium nitrate
(d) Potassium hydrogen phosphate
(b) Sodium carbonate
(e) Nickel(II) sulfate
(g) Phosphorus pentachloride
(j) Potassium dichromate
(h) Bromous acid
(k) Sulfur hexafluoride
(b) Chemical
(f) Physical
(c) Physical change
(g) Chemical
(e) 33.6 g
(d) Chemical
(h) Physical
(b) Compound
(c) Heterogeneous mixture
(e) Compound
(f) Homogeneous mixture
(h) Heterogeneous mixture
diameter = 1.30 cm
(b) Na3PO4
(h) H2S
Mass No.
25
31
63
108
207
# Protons
12
15
29
47
82
# Neutrons
13
16
34
61
125
# Electrons
10
15
29
46
80
Isotope
25
Mg2+
31
P
63
Cu
108
Ag+
207
Pb2+
(c) Silicon tetrafluoride
(f) Chromium(III) chloride
Hexahydrate
(i) Iron(III) hydroxide
(l) Periodic acid
9.
(a) Ca(OCl)2
(g) (NH4)2SO4
(c) H3PO4
(d) Pb(C2H3O2)2
(i) CuSO4.5H2O (j) B2O3
10.
(a) Empirical formula = C7H6O2 = Molecular formula
(b) 64.83% C; 13.60% H and 21.57% O; empirical formula = C4H10O
11.
(a) (NH4)2Cr2O7(s)  Cr2O3(s) + N2(g) + 4H2O(g)
(b) Ca(s) + 2H2O(l)  Ca(OH)2(aq) + H2(g)
12.
(a) C4H10O(l) + 6 O2(g)  4CO2(g) + 5H2O(g)
(b) 4NH3(g) + 5 O2(g)  4NO(g) + 6H2O(g)
(c) 3Ca(NO3)2(aq) + 2Na3PO4(aq)  Ca3(PO4)2(s) + 6NaNO3(aq)
13.
(a) Mass or O2 consumed = 1.21 x 103 g
(b) Mass of CO2 produced = 1.06 x 103 g;
(e) CCl4
(k) KMnO4
(f) Li2CO3
(l) Ba(OH)2
Mass of H2O produced = 490. G
14.
(a) Mole of H3PO4 = 2.50 moles; mole of NH3 = 6.75 moles; NH3 is the limiting reactant;
(b) Mass of (NH4)3PO4 = 336 g (at 100% yield); (c) = 307 g (at 91.5% yield;
(d) % yield = 94.6%;
(e) Mass of H3PO4 unreacted = 24.4 g
15.
(a) Mass of H2O = 1.35 g; mole of H2O = 0.0749 mole;
(b) Mass of Mg(OH)2 in mixture = 4.37 g; % of Mg(OH)2 in mixture = 87.4%
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