chem lecture wk 2 hw questions and answers
A chemical container measures 1 ft×1 ft×12 in. Calculate the volume of the container in cubic feet.
1 ft3 First, convert the last dimension from inches to feet: 12 in.×1 ft12 in.=1 ft Then, multiply to find the volume of the container: 1 ft×1 ft×1 ft=1 ft3
The engineer's model of a sugar factory has a floor area of 30 inches by 52 inches. The floor area of the model is __________ square feet.
10.8 This can be calculated by multiplying the dimensions of the model in inches and then converting into square feet, being sure to square the inch-to-feet conversion factor. 30 in.×52 in.×(1 ft12 in.)2=10.8 ft2
Mercury has a density of 13.56 g per cubic centimeter. Convert the density to kilograms per cubic meter.
13,560 kgm3 This problem requires using two different conversions: grams to kilograms and centimeters to meters. Since the starting units have grams in the numerator, use the conversion factor 1 kg1000 g to obtain kilograms in the numerator. The starting units have cubic centimeters in the denominator, so use the cubed conversion factor (100 cm1 m)3 to obtain cubic meters in the denominator. 13.56 gcm3×1 kg1000 g×(100 cm1 m)3=13560 kgm3
How many kilograms does a 40.0 lb-bag of cat food weigh? (1 lb=454 g)
18.2 kg We use dimensional analysis to convert between different units of measurement by multiplying a value by one or more fractions that are equal to one to change the way the value is expressed. Begin by starting with the value of 40.0 lb and multiply by a fraction that is equal to one that we are already aware of: 40.0 lb×454 g1 lb When we multiply this value of 40.0 lb by this fraction, we can see that the units cancel, just like an algebraic variable: 40.0 lb×454 g1 lb We repeat this process with a different conversion until we end up with the desired unit of kg: 40.0 lb×454 g1 lb×1 kg1000 g=18.16 kg The answer should have three significant figures, so round to 18.2 kg.
The temperature of a substance changes by 1K. This is equal to a temperature change of ________?
1∘C Looking at the image above, we can see that the freezing temperature of water on the Kelvin scale is 273.15 K, and its boiling temperature is 373.15 K. Notice that the numerical difference in these two reference temperatures is 100, the same is true for the Celsius scale. Water freezes at 0∘C and boils at 100∘C which is a difference of 100 in magnitude. This means that 1 K is equivalent to 1∘C in magnitude. This makes the conversion between the Celsius and Kelvin quite easy.
Which conversion factor would NOT be used in converting m/s into km/hr?
24hrs/day
Jacob takes 7 classes, each 50.00 minutes long, every day of the 5 day school week. How many hours per week does he spend in class?
29.17 hours per week The question is asking to convert the quantity 7classesschool day to the units hours of classweek. Use conversion factors that cancel the given units and leave the desired units. To convert from classes to hours of class, multiply by the conversion factor 50.00minutes of class1class to cancel classes and leave minutes of class, and then multiply by the conversion factor 1hour of class60minutes of class. To convert from school days to weeks, use the relationship 1week=5school days to write the conversion factors 5school days1week. This conversion factor cancels school days in the denominator and leaves weeks in the denominator. Now multiply to find the answer. 7classesschool day×50.00minutes of class1class×1hour of class60minutes of class×5school days1week=29.1667hours of classweek When we multiply or divide, our answer should have the same number of significant figures as the fewest significant figures. In this calculation, all of conversions are exact numbers except for the 50.00 minutes per class, so the final answer has four significant figures. Round to the correct number of significant figures: 29.17hours of classweek.
What is 0.29 km in mm?
290,000 mm There are 1000 meters in 1 kilometer and 1000 millimeters in 1 meter, so there are 1,000,000 millimeters in a kilometer. Dimensional analysis can involve 103 m1 km×103 mm1 m or can simply be 106 mm1 km.
35gigatons equals __________.
3.5×1010tons The prefix "giga" means 109, so it can be written as the following. 35gigaton=35×109tons To write the number in scientific notation, the decimal part must be between 1 and 10. Move the decimal point in 35 to the left one place, and, since this makes the number smaller by a power of 10, add 1 to the exponent on 10 to compensate.35×109tons=3.5×1010tons.
One year consists of 365 days. This is closest to how many seconds? (Remember the following conversion factors: kilo (103), mega (106), giga (109), and tera 1012.)
31.5 megaseconds One year is 365 days and each day has 24 hours. 365 days×24 hoursday×60 minuteshours×60 secondsminute=31,536,000 seconds Writing it in scientific notation gives: 31,536,000 seconds=3.1536×107 seconds. Reviewing the values of the prefixes, the exponential factor, 106, can be replaced by "mega," which is the only prefix that has the correct order of magnitude (maximum place value). 3.1536×107 seconds≈31.5 megaseconds
If we wish to convert a value in years into days, a conversion factor we could use would be:
365 days/1 year. The top and the bottom must be equal to each other, so 365 days and 1 year, as those represent the same length of time. In addition, days must be on top and years on the bottom so that we can appropriately cancel out the existing unit.
The circumference of the earth is approximately 40 million meters. This is closest to:
40 megameters 1,000,000 meters is equal to 1 megameter. 40,000,000 meters is then equal to 40 megameters.
A cylinder has a volume of 3 cubic feet. What is the volume in cubic inches?
5184 in.3 To convert cubic feet to cubic inches, use the cubed conversion factor for feet to inches. 3 ft3×(12 in.1 ft)3=5184 in.3
If you are traveling at 49.00 miles per hour, what is your speed in feet per second? (1 mile=5280 ft)
71.87 ft s Use dimensional analysis to convert miles per hour to feet per second by lining up units so that they cancel. 49.00mileshour×1hour60 min×1 min60 seconds×5280 feetmile=71.87feetsec
Which of the following statements BEST describes the SI system of unit?
An expansion of the metric system. The SI system is used in the scientific and medical fields and is an expanded form of the metric system.
The temperature scale we use most frequently in chemistry labs is:
Celsius The Kelvin scale is used most often in equations because it is an absolute temperature scale, but Celsius is most often used in the lab. Fahrenheit is rarely used in the field of chemistry.
An LCD TV was put in a box of size 12×24×24 inches. What is the volume of the box in cubic feet?
For this question, it is easier to convert each dimension to feet and then calculate the volume. (12 in.×1 ft12 in.)×(24 in.×1 ft12 in.)×(24 in.×1 ft12 in.)=1 ft×2 ft×2 ft=4 ft3
Which statement BEST explains why temperature is an intensive property?
It is a property that is independent of the amount of matter in a sample. Temperature is an intensive property because it is independent of the amount of matter for a given sample.
What is significant about the temperature of 0K?
It is the temperature at which atoms stop moving. A temperature of 0K is absolute zero and is the point at which motion of atoms stop.
In which temperature scale is the boiling point of water represented by the largest number?
Kelvin The boiling point of water is 100 Celsius, 212 Fahrenheit, and 373 Kelvin. Therefore the boiling point of water is represented by the largest number on the Kelvin scale.
The density of titanium is 4506 kg per cubic meter. What is the density of titanium in grams per cubic centimeter? Do not include units in your answer.
This problem requires using two different conversions: kilograms to grams and meters to centimeters. Since the starting units have kilograms in the numerator, use the conversion factor 1000 g1 kg to obtain grams in the numerator. The starting units have cubic meters in the denominator, so use the cubed conversion factor (1 m100 cm)3 to obtain cubic centimeters in the denominator. 4506 kgm3×1000 g1 kg×(1 m100 cm)3=4.506 gcm3
The density of a particular steel alloy is 8050 kg per cubic meter. Convert the density to grams per cubic centimeter. Do not include units in your answer.
This problem requires using two different conversions: kilograms to grams and meters to centimeters. Since the starting units have kilograms in the numerator, use the conversion factor 1000 g1 kg to obtain grams in the numerator. The starting units have cubic meters in the denominator, so use the cubed conversion factor (1 m100 cm)3 to obtain cubic centimeters in the denominator. 8050 kgm3×1000 g1 kg×(1 m100 cm)3=8.050 gcm3
The bed of a large pickup truck has a carrying capacity of 2.5cubic yards. How much is the capacity in cubic inches? Use the conversion factor 1yard=36inches.
To convert cubic yards to cubic inches, use the cubed conversion factor. There are 3 feet in a yard and 12 inches in a foot, so 1yard=36inches. Multiply 2.5yd3 by (36in./yd)3. 2.5yd3×(36in./yd)3=116,640in.3
The speed of light is around 6.706×10^8 miles per hour. What is the speed of light in units of miles per minute? Round the answer to four significant figures. When reporting your answer in scientific notation format, use the multiplication symbol, ×, not the letter x
To find the speed of light in units of miles per minute, we must use the fact that 60min=1hr. 6.706×10^8mihr×1hr60min=1.118×107mimin Therefore, we find that the speed of light is approximately 1.118×10^7 miles per minute.
If 1in.=2.54cm, calculate the number of inches in 75.0cm.
Using the fact that 2.54cm=1in. we can use dimensional analysis to calculate the number of inches in 75.0cm as follows. 75.0cm×1in.2.54cm=29.53in. Therefore, after rounding to three significant figures, we find that there are about 29.5in. in 75.0cm.
Which is the longest distance? Select the correct answer below: a meter a kilometer a megameter a terameter
a terameter A terameter is 1012 meters, whereas a megameter is 106 meters and a kilometer is 103 meters.
Which operation is performed to convert a temperature given in degrees Celsius to a temperature in kelvin?
add 273 Kelvin and Celsius have a linear relationship, but not a proportional relationship. They do not have the same starting point, but they increase at the same rate. 0 K is absolute zero, which is about −273∘C, so to get Kelvin from Celsius, add 273.
What is the SI unit of "mole" used to measure?
amount of a substance The mole is an SI unit used to measure amount of a substance. It's similar to how a 'dozen' is an amount that means 12 of something.
Which prefix means one one-hundredth?
centi Deci is one tenth, milli is one one-thousandth, and kilo is one thousand.
Which of the following is NOT a base unit used in the SI system of measurement?
milliliter The second, the mole, and the meter are all SI base units. Milliliter is a prefixed unit, with the base unit of "liter."
Which of the following units is a derived SI unit (not one of the SI base units)?
newton Newtons are defined to be kg ms2. The other three units are base SI units.
Which is the shortest length of time? Select the correct answer below: one microsecond one nanosecond one millisecond one decisecond
one nanosecond A nanosecond is 10−9 seconds, whereas a microsecond is 10−6 seconds, a millisecond is 10−3 seconds, and a decisecond is 10−1 seconds.
In dimensional analysis, what is a conversion factor?
ratios of physical quantities used to compare desired units Conversion units are ratios of physical quantities used to compare between two desired units. They are not experimental or theoretical.
What is the standard SI unit for volume?
the cubic meter The cubic meter is the standard SI unit for volume. The foot and decimeter are units of length and the second is a unit of time.
What is the standard SI unit of mass? Select the correct answer below: the pound the meter the kilogram the gram
the kilogram The standard SI unit of mass is the kilogram. The gram and the pound are also units of mass but only the kilogram is the SI unit of mass. The meter is the SI unit of length.
How was the kilogram originally defined?
the mass of a liter of water The kilogram was originally defined to be the mass of one liter of water; however, there is some variance in this quantity with temperature and pressure. This is why a more rigid definition for the kilogram was adopted In the late 19th century, which defined the mass of one kilogram as the mass of a metal cylinder of platinum-iridium alloy, which is stored in France. More recently, in November of 2018, the kilogram was redefined in terms of Planck's constant, which is a fundamental constant of nature.
While the SI base unit of time is the second, what other unit can also be used?
years Although the second is the SI base unit of time, hours, days, and years can all be used as units of time. Kelvin is a unit of temperature, meter is a unit of length, and liter is a unit of volume.
Which of the following temperatures are equivalent to absolute zero (0 K)?
−273.15∘C −459.67∘F We can convert from Kelvin to Celsius using the following equation: ∘C=K−273.15 Therefore,0K−273.15=−273.15∘C We can convert from Celsius to Fahrenheit using the following equation: ∘F∘F=95×∘C+32=95×−273.15∘C+32=−459.67∘F Therefore, −273.15∘C and −459.67∘F show absolute zero on the Celsius and Fahrenheit scales.
