Answer:
. (3 pts each) Carry out the following operations, and express the answer with the appropriate number of significant figures:
a. 1.24056 + 75.8 =
1.24056
+75.8
77.04056 -> Round to tenths place: 77.0
b. 320.55 – (6104.5/2.3) =
320.55
-2654.1304
-2333.580 -> round to HUNDREDS place: -2300 or -2.3 x 103
c. (0.0045 x 20,000.0) + (2813 x 12) =
90.000
+33756.000
33846.000 -> round to TEN THOUSANDS place: 34000 or 3.4 x 104
The all-time record lowest temperature ever recorded on this planet is –57.63 oC (recorded on July 21, 1983 in Vostok, the Russian Antarctic station).
a. Express this temperature in oF.
oF = (9/5)oC + 32
= (9/5)(-57.63) + 32 = -71.734 oF à -71.73 oF
b. Express this temperature in Kelvins (K).
K = oC + 273.15
= -57.63 + 273.15 = 215.52 K à 215.52 K
3. (10 pts) A 26.27-g sample of a solid is placed in a flask. Toluene, in which the solid is insoluble, is added to the flask so that the volume of the solid and liquid together is 50.00 mL. The solid and liquid toluene together weigh 52.65 g. The density of toluene at the temperature of the experiment is 0.864 g/mL. What is the density of the solid?
solid + toluene = 52.65 g
solid = 26.27 g
Mass of toluene = 26.38 g toluene
26.38 g toluene x 1 ml toluene = 30.53241 mL toluene
0.864 g toluene
solid + toluene = 50.00 mL
toluene = 30.53241 mL
solid = 19.46759 mL
density of the solid = 26.27 g
19.46759 mL
= 1.34942 g/mL à 1.35 g/mL
4. (16 pts) Fill in the gaps in the following table:
Symbol
52Cr3+
107Ag+
75As3-
Protons
24
47
33
Neutrons
28
60
42
Electrons
21
46
36
Net Charge
3+
1+
3-
. (2 pts each) From this list of elements: Ar, H, Ga, Al, Ca, Br, Ge, K, O; pick the one that best fits each of the following descriptions. You may use each element only ONCE.
a. an alkali metal: K
b. an alkaline earth metal: Ca
c. a noble gas: Ar
d. a halogen: Br
e. a metalloid: Ge
f. a nonmetal listed in group IA: H
g. a metal that forms a 3+ ion: Al
h. a nonmetal that forms a 2- ion: O
i. an element that resembles aluminum: Ga
6. (1 pt each) Give the atomic symbol for the following elements:
a. calcium: Ca
b. sodium: Na
c. mercury: Hg
d. lead: Pb
3 pts each) Write a complete, balanced chemical equation for each of the following reactions:
a. Solid calcium carbide (CaC2) reacts with water to form an aqueous solution of calcium hydroxide and acetylene gas (C2H2).
HOPE THIS HELPS YOU OUT :3