Sig Figs, Electrons, Protons, Neutrons
14.7
A thief uses a bag of sand to replace a gold statue that sits on a weight sensitive alarmed pedestal. The bag of sand and statue have the exact same volume of 3.75L.
A) Calculate the mass of each object. Density gold= 19.3g/cm3 Density of sand = 3g/cm
B) Did the thief set the alarm off?
Gold - 3.38E4
Sand 5.25E3
YES
A hybrid SUV consumes fuel at a rate of 12.8km/L. How many miles can the car travel on 22.5 gallons of gas?
677 miles
Classify each property as a physical property or chemical property.
A) the tendency for silver to tarnish
B) the shine of chrome
C) the color of gold
D) the flammability of propane gas
Chemical
physical
physical
chemical
Compound 1 has a composition of 40% mass of element C and 60% mass of element D. Compound 2 is formed from the same element C & D. According to the law of multiple proportions which of the following compositions could be compound 2?
A) 22.3% C, 77.7% D
B) 33.3% C, 66.7% D
C) 57.1% C, 42.9% D
D) 60% C, 40% D
E) none of these
C) 57.1 % C, 42.9% D
Identify Mass #, #of electrons, protons, and neutrons of 208Pb
Mass # 208 electrons/protons - 82 neutrons 126
The density of air is 0.001225g/cm3. A room has dimensions of 2in by 5cm by 1ft. What is the mass of the air in grams?
5.08cm x 5cm x 30.48cm = V= 774.19cm3
Mass 0.9g
A 27.3 gram sample of H3Cl3 is made up of 5.2g of hydrogen. How many moles of Chlorine are in this sample?
0.623 moles H
Element X has two naturally occurring isotopes. X-68 with a mass of 68.9256amu and a natural abundance of 60.11%. X-71 has a mass of 70.9247 amu. Calculate the atomic mass of X?
69.72amu
A compound is found to be made up of carbon and oxygen. In sample 1, the mass of carbon is 24g and the mass of oxygen is 64 grams. In a second sample, the mass of carbon is 36g. What is the mass of oxygen in the second sample? Show that this result follows the law of definite proportions.
96.12g of oxygen.
64/24 = 2.67
96.12/36 = 2.67
6.75 x 5.903 x (5.489 - 5.01)
19
Block A of an unknown metal has a volume of 125cm3. Block B of a different metal has a volume of 105cm3. If block A has a greater mass than block B, what can be said of the relative densities of the two solid metals.
Block A density > Block B density
What is the molar mass of silver oxide?
Mass % of each element?
# of oxygen atoms in 3.52 grams of Ag2O?
mm Ag2O = 231.74
% Ag = 92.92%
%O = 6.90%
9.15E21 atoms of Cl
Upon decomposition one sample of magnesium bromide (MgBr2) produced 1.75kg of mg and 2.25kg of bromide. A second sample produced 1.5g of mg. How much bromide (in grams) was produced in the second sample. What is the mass % of mg and bromide in the original sample?
1.9g Br
56.25% Br
43.75% MG
Transition metals are known to form a variety of oxides with the metal being found in different oxidation states. Starting with 4 grams of a sample of the oxide the following data is obtained. Assume compound A is Z2O. What are the empirical formulas for B, C, and D?
X oxide Amount of Z in oxide
A 3.200g
B 3.000g
C 2.667g
D 2.500g
A) Z2O
B) Z6O4
C) Z2O2
D) Z4O5
What is the charge on iron (Fe) if it has 26 protons and 28 electrons?
2+
Glycerol is a syrupy liquid often used in cosmetics and soaps. A 2.50L sample of pure glycerol has a mass of 3.15E7 micrograms. What is the density of the glycerol in grams per cubic cm?
D= 31.5g/2500mL
D=0.013g/cm3
A 40gram sample is made up of hydrogen, oxygen, and sulfur. If half the sample is made up of oxygen and 4 grams of hydrogen. What are the mass fractions and mass % of each element?
.4 Sulfur 40%
.1 Hydrogen 10%
.5 Oxygen 50%
A mineral, apatite, has a chemical formula Ca5(PO4)3(OH). How many phosphate ions are in the sample of apatite that contain 325 micrograms of hydrogen?
5.83E20 ions of phosphate.
A 6.74g sample of magnesium and chlorine contains 2.95g of chloride.
a) calculate the mass of chloride
b) calculate the mass fractions and mass % of each element
c) how many grams of chloride would be in a 3275g sample of the same compound?
3.79g of chloride
mass fractions and %
Cl - 0.5623 56.23%
Mg - 0.4377 43.77%
1841.5g Cl
30K
What is the mass #?
How many protons electrons and neutrons?
11 neutrons
19 protons and electrons.
Mass number 30
A tank contains 5 gallons of helium gas. The total mass of the helium in the tank is 33 grams. Calculate the density of the helium in grams per liter (g/mL).
The density of helium in the tank is approximately 0.00174 g/mL.
A vitamin suspension for infants contains 150mg/mL suspension. The recommended dose is 12mg/kg body weight. How many mL of this suspension should be given to an infant that weighs 20lbs?
4.4mL
Compound Z has two naturally occurring isotopes. Z-22 has a mass of 102.34amu and Z-33 has a mass of 101.475 amu. Calculate the % abundance of each isotope. Assume the atomic mass of Z is 102.01amu.
Z-22 = 61.8%
Z-33 = 38.2%
If elements A and B react to form 2 compounds. the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers. If we assume compound A has the empirical formula Li2O, what is the empirical formula for compounds B and C?
Mass of Li that combines with 1 gram of Oxygen
Compound A 0.4375g
Compound B 0.8750g
Compound C 1.7500g
A - Li2O
B - Li2O2
C - Li2O4