Measurements - AP Chemistry
Card 0 of 336
What unit will be used to denote temperature in thermochemistry?
What unit will be used to denote temperature in thermochemistry?
Temperature is the measure of the average kinetic energy of a system. Kelvin is the SI unit for temperature, and must be used because it is the only scale that does not have any negative numbers possible. At zero Kelvin (absolute zero) and there is absolutely no movement in the system, down to the atomic level.
While temperature is a means of measuring energy in a system, actual heat energy has the unit Joules.
Temperature is the measure of the average kinetic energy of a system. Kelvin is the SI unit for temperature, and must be used because it is the only scale that does not have any negative numbers possible. At zero Kelvin (absolute zero) and there is absolutely no movement in the system, down to the atomic level.
While temperature is a means of measuring energy in a system, actual heat energy has the unit Joules.
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Which of the following measurements contains 4 significant figures?
Which of the following measurements contains 4 significant figures?
1. Any digit with a value 1-9 is always a significant figure
2. Any 0 between two digits 1-9 is always significant
3. If a number is greater than 1 and does not have a decimal point a 0 at the end is not significant because it is a tailing zero
4. If a number is less than 1 any 0 before a digit 1-9 is not significant because it is a leading zero
5. If there is a decimal point in any number, any 0 that follows a non-zero digit is always significant.
Thus, 
has 4 significant figures. The first 0 is not significant because of rule 4. The digits 1, 9, and 6 are always significant (rule 1) and the last 0 is also significant because there is a decimal point and that 0 follows a non-zero digit (rule 5).
1. Any digit with a value 1-9 is always a significant figure
2. Any 0 between two digits 1-9 is always significant
3. If a number is greater than 1 and does not have a decimal point a 0 at the end is not significant because it is a tailing zero
4. If a number is less than 1 any 0 before a digit 1-9 is not significant because it is a leading zero
5. If there is a decimal point in any number, any 0 that follows a non-zero digit is always significant.
Thus,
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Which has the larger unit listed first?
Which has the larger unit listed first?
The following prefixes are ranked in order from largest to smallest with the power of 10 that the unit represents: peta (P) 
> tera (T) 
> giga (G) 
> mega (M) 
> kilo (k) 
> hecta (H) 
> deca (D) 
> unit > deci (d) 
> centi (c) 
> milli (m) 
> micro 
> nano (n) 
> pico (p) 
> femto (f) 
. Thus a microsecond is one thousand times longer than a nanosecond.
The following prefixes are ranked in order from largest to smallest with the power of 10 that the unit represents: peta (P)
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The measurement of 
is equal to which of the following?
The measurement of
Units in the metric system can be converted using the correct factor of 10.
Units in the metric system can be converted using the correct factor of 10.
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A certain metal is weighed on a balance in a weighing boat. Before the metal is added, the mass of the weigh boat is recorded at 
. The final mass of the weigh boat and the metal is 
. The metal is added to a graduated cylinder filled with water to 
. After the metal is added to the water the graduated cylinder reads 
.
What is the density of the metal?
A certain metal is weighed on a balance in a weighing boat. Before the metal is added, the mass of the weigh boat is recorded at
What is the density of the metal?
Density is equal to the mass of the object divided by the volume.
The mass of the metal is figured out by taking the mass of the metal and the weighboat 
and subtracting the weighboat 
The volume of the water is calculated by the displacement of the water so take the final volume and subtract the initial volume.
The density of the metal is calculated by taking the mass divided by the volume.
after rounding to 3 significant figures.
Density is equal to the mass of the object divided by the volume.
The mass of the metal is figured out by taking the mass of the metal and the weighboat
The volume of the water is calculated by the displacement of the water so take the final volume and subtract the initial volume.
The density of the metal is calculated by taking the mass divided by the volume.
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An object is measured to be 
tall. How tall is the object in inches?
An object is measured to be
You must use equalities and dimensional analysis to solve for the correct answer:
Each equality allows you to write a conversion factor 2 ways:
Example: 
can be written as
and 
To cancel out units if there is a unit on top it must be cancelled out by the same unit on the bottom.
To solve you must cancel out units until you get to the proper unit
You must use equalities and dimensional analysis to solve for the correct answer:
Each equality allows you to write a conversion factor 2 ways:
Example:
To cancel out units if there is a unit on top it must be cancelled out by the same unit on the bottom.
To solve you must cancel out units until you get to the proper unit
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How many atoms are in 1 mole of H2?
How many atoms are in 1 mole of H2?
This question requires an understanding of what avogadro's number actually represents. Avogadro's number, 6.022 * 1023 is the number of things in one mole. The question indicates that there is 1 mole of H2. Thus there are 6.022 * 1023 molecules of H2. However the question is asking for the amount of atoms in 1 mole of H2. Thus we must consider the makeup of an H2 molecule, where we see that it is a diatomic molecule. Thus we must multiply 6.022 * 1023 by 2 to calculate the number of individual atoms present in 1 mole of H2. We find our answer to be 1.2044 * 1024.
This question requires an understanding of what avogadro's number actually represents. Avogadro's number, 6.022 * 1023 is the number of things in one mole. The question indicates that there is 1 mole of H2. Thus there are 6.022 * 1023 molecules of H2. However the question is asking for the amount of atoms in 1 mole of H2. Thus we must consider the makeup of an H2 molecule, where we see that it is a diatomic molecule. Thus we must multiply 6.022 * 1023 by 2 to calculate the number of individual atoms present in 1 mole of H2. We find our answer to be 1.2044 * 1024.
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A chemist has 
of 
.
How many molecules of 
does she have?
A chemist has
How many molecules of
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What is the mass of 
particles of 
?
What is the mass of
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How many atoms are in 
of calcium?
How many atoms are in
In order to determine how many atoms are in this sample, we need to convert this sample into moles. Calcium has a molar mass of 
grams per mole.
Avogadro's number tells us that there 
atoms in one mole of any element. We can use this conversion to find the total number of atoms in the sample.
In order to determine how many atoms are in this sample, we need to convert this sample into moles. Calcium has a molar mass of
Avogadro's number tells us that there
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How many hydrogen atoms are in 46.3 g of ethanol, 
?
How many hydrogen atoms are in 46.3 g of ethanol,
To determine the number of hydrogen atoms, divide the mass of ethanol by its molar mass to get moles of ethanol.
Multiply this by six atoms of hydrogen per molecule of ethanol and by Avogadro's number to get the number of hydrogen atoms.
To determine the number of hydrogen atoms, divide the mass of ethanol by its molar mass to get moles of ethanol.
Multiply this by six atoms of hydrogen per molecule of ethanol and by Avogadro's number to get the number of hydrogen atoms.
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How many hydrogen atoms are present in 500 mL of water at room temperature?
How many hydrogen atoms are present in 500 mL of water at room temperature?
Use the density of water, the molar mass of water, and Avogadro's number to calculate the number of molecules of water.
We have 500mL of water. Use the density to convert this to grams; then use the molar mass of water to convert this to moles.
There are two moles of hydrogen atoms per one mole of water.
Finally, multiply by Avogadro's number.
Use the density of water, the molar mass of water, and Avogadro's number to calculate the number of molecules of water.
We have 500mL of water. Use the density to convert this to grams; then use the molar mass of water to convert this to moles.
There are two moles of hydrogen atoms per one mole of water.
Finally, multiply by Avogadro's number.
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How many molecules are in 
?
How many molecules are in
According to Avogadro's law, each mole of a compound contains 
. Use dimensional analysis to find the number of molecules in 
.
According to Avogadro's law, each mole of a compound contains
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How many atoms are there in 47.5g of boron?
How many atoms are there in 47.5g of boron?
To do this problem we have to first convert grams to moles, then moles to atoms using Avogadro's number:
To do this problem we have to first convert grams to moles, then moles to atoms using Avogadro's number:
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How many moles of carbon are in a sample of 
atoms?
How many moles of carbon are in a sample of
To solve, we need to convert atoms to moles using Avogadro's number:
To solve, we need to convert atoms to moles using Avogadro's number:
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How many atoms of sodium are in three moles of 
?
How many atoms of sodium are in three moles of
To answer this question, we have to find the number of moles of sodium in this compound. Note that there are two sodium atoms per molecule. Then, multiply the total moles of sodium by Avogadro's number.
To answer this question, we have to find the number of moles of sodium in this compound. Note that there are two sodium atoms per molecule. Then, multiply the total moles of sodium by Avogadro's number.
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You have a neutral balloon. If you were to add 21,000 electrons to it, what would its net charge be?
= charge of one electron
You have a neutral balloon. If you were to add 21,000 electrons to it, what would its net charge be?
The elemental charge is the magnitude of charge, in Coulombs, that each electron or proton has. Because electrons have a negative charge, don't forget to add a negative sign into the equation.
When you convert the answer to microcoulombs, the answer is 
:
The elemental charge is the magnitude of charge, in Coulombs, that each electron or proton has. Because electrons have a negative charge, don't forget to add a negative sign into the equation.
When you convert the answer to microcoulombs, the answer is
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Determine the number of sodium atoms in a 
block of sodium chloride.
Determine the number of sodium atoms in a
Use dimensional analysis:
Use dimensional analysis:
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A container has 
molecules of gas in it. How many moles of the gas are in the container?
A container has
Avogadro's number tells us how many molecules of gas are in one mole of the container. We are essentially doing a unit conversion from "number of molecules" to moles -
Avogadro's number tells us how many molecules of gas are in one mole of the container. We are essentially doing a unit conversion from "number of molecules" to moles -
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Convert the given value to scientific notation, rounding to six significant figures.
Convert the given value to scientific notation, rounding to six significant figures.
Scientific notation is used to simplify exceptionally complex numbers and to quickly present the number of significant figures in a given value. The value is converted to an exponent form using base ten, such that only a single-digit term with any given number of decimal places is used to represent the significant figures of the given value. Non-significant zeroes can be omitted from the leading term, and represented only in the base ten exponent.
We are told that the final value must have six significant figures, so there will be six digits multiplied by the base ten term. We take only the first six digits, rounding the final digit depending on the final term; in this case we round up (123457).
To generate the single-digit leading term the decimal must be placed after the 1 (1.23457). Then count the digits to the left of the decimal to determine the change in decimal placement (the decimal moves past the 1 only). Our ten will be raised to the power of negative one because there is only one digit to the left of the final decimal placement.
Our final answer is 
.
Scientific notation is used to simplify exceptionally complex numbers and to quickly present the number of significant figures in a given value. The value is converted to an exponent form using base ten, such that only a single-digit term with any given number of decimal places is used to represent the significant figures of the given value. Non-significant zeroes can be omitted from the leading term, and represented only in the base ten exponent.
We are told that the final value must have six significant figures, so there will be six digits multiplied by the base ten term. We take only the first six digits, rounding the final digit depending on the final term; in this case we round up (123457).
To generate the single-digit leading term the decimal must be placed after the 1 (1.23457). Then count the digits to the left of the decimal to determine the change in decimal placement (the decimal moves past the 1 only). Our ten will be raised to the power of negative one because there is only one digit to the left of the final decimal placement.
Our final answer is
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