Physical Science Midterm 2 Exam
Suppose you have an Avogadro's number of oxygen atoms. How many grams does this represent?
Report your answer to two decimal places. - correct answer 16.00 grams
A certain combustion reaction generates 5.00 moles of carbon dioxide. How many grams does this
represent?Report your answer to 3 significant figures. - correct answer 220 grams
CO2: 44.0
44 * 5 = 220
Describe the shape of a CH4 molecule. - correct answer Tetrahedral
What is the mass of one atom of carbon? - correct answer 1.99 x 10^-23g
12/(6.02 x 10^23)
An element has two naturally-occurring isotopes. The mass numbers of these isotopes are 125.00 u
and 127.00 u, with natural abundances of 55% and 45%, respectively. Calculate its average atomic
mass. Report your answer to 2 decimal places. - correct answer 125.90 u
(125.00)(0.55) + (127.00)(0.45)= 125.90
How many atoms are contained in 4.50 g of carbon? - correct answer 2.3 x 10^23
4.50/12= 0.375
0.375 x (6 x 10^23) = 2.3 x 10^23
Calculate the molar mass of CO2. Report your answer to 2 decimal places. - correct answer 44.01
g/mol
Calculate the mass% of O in a molecule of water, H2O. - correct answer 88.81%
, 16.00/18.016 = 0.8881
0.8881 x 100= 88.81%
One year, a herd of cattle released 4.34 metric tons of CH4 (methane) into the atmosphere. How
many metric tons of carbon did this methane contain? - correct answer 4.34 x 1000 x 1000 = 4.34
x 10^6/16g/mol= 271250 mol
271250 mol x 12g/mol= 3,255,000g
3,255,000/10^6= 3.26 metric tons C
Choose from the conversion factors given to complete the following diagram of amount-mass-
number relationships for a compound. - correct answer check screenshot
Choose from the conversion factors given to complete the following diagram of amount-mass-
number relationships for two species, A and B, in a chemical reaction. - correct answer check
screenshot
Choose from the conversion factors given to complete the following diagram of amount-mass-
number-volume relationships for a solution. - correct answer check screenshot
Predict the molecular shape for each of these compounds. Remember to consider all of the outer
electrons before you make your choice. - correct answer Tetrahedral- Methane
Trigonal Pyramidal- Ammonia
Trigonal Planar- Sulfur Trioxide
Bent- Water, Ozone
Linear- Carbon Dioxide
Predict the molecular shape for each of these compounds. Remember to consider all of the outer
electrons before you make your choice. - correct answer Tetrahedral- Dichlorodifluoromethane
Trigonal Pyramidal- Ammonia
Bent- Sulfur Dioxide, Nitrogen Dioxide
Linear- Carbon Dioxide, Nitrogen
Many different processes contribute to maintaining the Earth's energy balance. Sort each example
into the most appropriate place in the energy balance. - correct answer check screenshot
Suppose you have an Avogadro's number of oxygen atoms. How many grams does this represent?
Report your answer to two decimal places. - correct answer 16.00 grams
A certain combustion reaction generates 5.00 moles of carbon dioxide. How many grams does this
represent?Report your answer to 3 significant figures. - correct answer 220 grams
CO2: 44.0
44 * 5 = 220
Describe the shape of a CH4 molecule. - correct answer Tetrahedral
What is the mass of one atom of carbon? - correct answer 1.99 x 10^-23g
12/(6.02 x 10^23)
An element has two naturally-occurring isotopes. The mass numbers of these isotopes are 125.00 u
and 127.00 u, with natural abundances of 55% and 45%, respectively. Calculate its average atomic
mass. Report your answer to 2 decimal places. - correct answer 125.90 u
(125.00)(0.55) + (127.00)(0.45)= 125.90
How many atoms are contained in 4.50 g of carbon? - correct answer 2.3 x 10^23
4.50/12= 0.375
0.375 x (6 x 10^23) = 2.3 x 10^23
Calculate the molar mass of CO2. Report your answer to 2 decimal places. - correct answer 44.01
g/mol
Calculate the mass% of O in a molecule of water, H2O. - correct answer 88.81%
, 16.00/18.016 = 0.8881
0.8881 x 100= 88.81%
One year, a herd of cattle released 4.34 metric tons of CH4 (methane) into the atmosphere. How
many metric tons of carbon did this methane contain? - correct answer 4.34 x 1000 x 1000 = 4.34
x 10^6/16g/mol= 271250 mol
271250 mol x 12g/mol= 3,255,000g
3,255,000/10^6= 3.26 metric tons C
Choose from the conversion factors given to complete the following diagram of amount-mass-
number relationships for a compound. - correct answer check screenshot
Choose from the conversion factors given to complete the following diagram of amount-mass-
number relationships for two species, A and B, in a chemical reaction. - correct answer check
screenshot
Choose from the conversion factors given to complete the following diagram of amount-mass-
number-volume relationships for a solution. - correct answer check screenshot
Predict the molecular shape for each of these compounds. Remember to consider all of the outer
electrons before you make your choice. - correct answer Tetrahedral- Methane
Trigonal Pyramidal- Ammonia
Trigonal Planar- Sulfur Trioxide
Bent- Water, Ozone
Linear- Carbon Dioxide
Predict the molecular shape for each of these compounds. Remember to consider all of the outer
electrons before you make your choice. - correct answer Tetrahedral- Dichlorodifluoromethane
Trigonal Pyramidal- Ammonia
Bent- Sulfur Dioxide, Nitrogen Dioxide
Linear- Carbon Dioxide, Nitrogen
Many different processes contribute to maintaining the Earth's energy balance. Sort each example
into the most appropriate place in the energy balance. - correct answer check screenshot
