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Exam 1 Key
CURVE
A 100-
B 89-
C 79-
D 69-
B D A C E B D A E C B all all A E D B E A C
- Which one of the following ways would best determine whether a colorless liquid is pure water or salt water (you cannot taste it). Weigh it. If it weighs more, it is salt water. More than what? Evaporate it. If salt crystals form, it is salt water. See if it burns. Salt water will burn. Ridiculous Smell it. Salt water smells salty. Only if it actually gets into your nose. Look at it under the microscope to see if there are salt crystals in it. All of the salt crystals will be dissolved. A solid white substance A is heated strongly in the absence of air. It decomposes to form an off-white solid B and a gas C. The gas has the same properties as the product obtained when carbon is burned in excess oxygen. About solid A and gas C, we can say By definition, any substance that decomposes is a compound, so A is a compound. Combustion of carbon (+ oxygen) produces the compound CO 2 Both A and C are elements. A is an element and C is a compound. A is a compound and C is an element. Both A and C are compounds. Nothing; not enough data. Which one of the following correctly expresses the volume 3.35 X 10-8^ m^3? The easiest way to do this is to take the cube root of the given value: (3.35E-8 m 3 )1/3^ = 3.22E-3 m = 3.22 mm. Now cube the result: (3.22 mm) 3 = 33.5 mm 3 33.5 mm 3
335 cm 3 3.35 mL
33.5 mm 3
1.50 mm 3
A temperature of -37 o^ C on the Kelvin (absolute) temperature scale is
-37 o^ C + 273 = 236 K 114 K 273 K 236 K 304 K 291 K Which one of the following numbers has 4 significant figures? 0.0590 This one has 3 0.0015 This one has 2 2000.1 This one has 5
3.29 X 10 3 This one has 3
Convert the velocity of a snail (5.68 cm/min) to units of km/hr. 5.68 cm/min (60 min/hr) (1E-2 m/cm) (1 km/1E3 m) = 3.41E-3 km/hr
6.21 X 10 2 km/hr
3.41 X 10 -3^ km/hr
8.37 X 10 -4^ km/hr
1.28 X 10 5 km/hr
5.11 X 10 -2^ km/hr A student finds that 15.20 g of nitrogen will react with 34.74 g of oxygen. Calculate the mass of oxygen per gram of nitrogen in this compound. (34.74 g oxygen)/(15.20 g nitrogen) = 2.29 g oxygen/g nitrogen
(Crx^ ) 2 (CO 3 2-) 3 ; charge balance: 2x + 3(-2) = 0 => x = +3; Cr 3+^ == chromium (III), CO 3 2-^ == carbonate
chromium carbon oxide chromium(III) carbonate chromium carbonate chromium(II) carbonate chromium carboxide Which one of the following names is not correct? iron(III) carbonate - Fe 2 (CO 3 ) 3
Copper(I) oxide - Cu 2 O
zinc nitrate - Zn(NO 3 ) (^2)
sodium hypochlorite - NaClO (^2)
potassium peroxide - K 2 O (^2)
What is the chemical formula of magnesium phosphite?
Mn 3 (PO 4 ) (^2) Mn is manganese, and PO 4 3-^ is phosphate
MnPO 3
Mg 3 (PO 3 ) (^2)
Mg 3 PO 4
Mn(PO 4 ) (^2)
Balance the following chemical equation with the smallest whole number coefficients: a Mg 3 N 2 (s) + b HCl(aq) --> c MgCl 2 (aq) + d NH 4 Cl(aq)
a: 1 b: 8 c: 3 d: 2 a: 2 b: 6 c: 2 d: 3 a: 1 b: 5 c: 4 d: 1 a: 3 b: 6 c: 7 d: 5 a: 2 b: 4 c: 4 d: 6 Write the balanced chemical reaction described by these words: solid potassium chlorate decomposes on heating to form solid potassium chloride and oxygen gas.
Potassium chlorate is (K+^ )(ClO 3 - ) == KClO 3. Potassium chloride is (K+^ )(Cl -^ ) == KCl. Oxygen gas is diatomic O 2.
2KClO 2 (s) --> 2KClO(s) + O 2 (g)
2KClO 4 (s) --> 2KClO(s) + 3O 2 (g)
2KClO(s) --> 2KCl(s) + O 2 (g)
KClO 4 (s) --> KClO 3 (s) + O(g)
2KClO 3 (s) --> 2KCl(s) + 3O 2 (g)
Which one of the following unbalanced chemical reactions is not correctly characterized by reaction type? combustion: C 3 H 6 (g) + O 2 (g) --> CO 2 (g) + H 2 O(l)
decomposition: NH 4 NO 3 (s) --> N 2 O(g) + H 2 O(l)
combustion: C 5 H 6 O(l) + O 2 (g) --> CO 2 (g) + H 2 O(l)
decomposition: K 2 O(s) + H 2 O(l) --> KOH(aq) Combination
combination: N 2 (g) + H 2 (g) --> NH 3 (g)
Calculate the percentage by mass of oxygen in chromium(III) nitrate.
(Cr3+^ )(NO 3 -^ _) 3 == Cr(NO 3 ) 3 FW = (52.00) + 3(14.01 + 316.00) = 238.01 g/mol Oxygen mass = 916.00 = 144.00 g/mol mass ratio: 144.00/238.01 = 0.6050 = 60.50 %_* 72.91 % 60.50 % 47.61 % 36.18 % 83.22 % What is the molar mass of cholesterol if 1.05 mmol (millimole) weighs 406 mg? 406 mg/1.05 mmol = 387 mg/mmol = 0.406 g/0.00105 mol = 387 g/mol 204 g/mol 129 g/mol
LR(NH 3 ): 0.2924-4x = 0 => x = 0. LR(O 2 ): 0.1006-5x = 0 => x = 0. Oxygen is the limiting reagent, ammonia is the reagent in excess. The final reaction table is:
Fn Fm
NH 3 O 2 NO H 2 O
FW 17.03 32.
Im 4.98 3. In 0.2924 0.
∆ n -4x -5x
Fn 0.2119 0 Fm 3.61 0
1.77 g O 2
2.58 g NH (^3)
3.61 g NH (^3)
3.01 g O 2
0.94 g O 2
