the amount of a substance that contains 6.02 x 10 (exponent 23) particles
The particle that represents a substance depends on what?
type of substance
What are atoms?
representative particles for monoatomic elements
what are molecules?
representative particles for molecular compounds and diatomic elements
what are formula units?
representative particles for ionic compounds
What is avagadros number?
the number of particles in a mole of a substance
What is molar mass?
the mass of one mole of a substance
How can a mole be defined?
it can be defined in terms of the number of particles in a substance or by the grams of the substance
What can the mole be used as?
a means of converting among different units
what is the molar volume?
the volume of one mole of any gaseous substance at standard conditions
what is the molar volume of a gas at 0 C and 1atmosphere of pressure?
what is the mole?
the number of atoms of an elements equal to the number of atoms in exactly 12g of Carbon-12
what is an atom for scientists?
a unit of measurement
the sum of the atomic masses of all the atoms in a compound
the lowest whole number ratio of elements in an ionic compound
the atomic mass of an atom is based on a comparison with what?
a mole of ____ contains 6.02 x10 23 ___
any element; atoms
a mole of an ___ compound contains 6.02 x 10 23 ___
ionic compound; molecules
the molar mass of any substance in grams is always equal to what?
the formula mass in amu
one mole of HNO3 contains how many atoms of oxygen?
how would you calculate the number of moles present in a given mass of a substance?
divide the mass of the substance by its molar mass
how would you calculate the number of particles present in a given number of moles of a substance?
multiply avagadros number by the number of moles
How would you calculate the number of particles present in a given mass of a substance?
take the given mass of the substance and divide it by the molar mass, and multiply the moles by Avagadros Number
one of the many measurements used to describe substances in chemistry is what?
because the actual mass of a single atom is so small what is used?
amu's are used to describe the mass of an atom
because the actual mass of a single atom is so ____, what is used?
small;amu's are used
is knowing the mass of one atom or one molecule in atomic mass units important in a lab? Explain.
no, it isnt practical. instead the gram is the desired unit of mass
in order to establish the relationship between mass and grams what must scientists do?
1. identify what they already knew about atoms and mass 2. using the relationship between masses of different elements, they
what relationship did scientists discover between the masses of different elements?
as long as the mass of the elements aer in the same ratio as their atomic masses, there are equal numbers of atoms of each element.
why are amu's used to dscribe the mass of an atom/
because the actual mass of a single atom is so small
the mass of an atom/ mass assigned to carbon-12
As far as the masses of the element samples are in the ___ ratio as their atomic masses, there are equal numbers of ___
a mole of any element is defined as what?
the number of atoms of that element equal to the number of atoms in exactly 12.0 grams of carbon
how many atoms are in a mole?
6.02 x 10 to the 23
the mole establishes a relationship between what?
amu and gram
the mass ( in grams) of one mole of a substance is equal to what?
its atomic mass or formula mass in amu's
a mole is basically what
a group of atoms
what kind of particles can the mole count?
atoms, molecules or formula units
the number of ___ in one mole is always 6.02 x 10 23
what is an atom?
the smallest particle of an element that retains the identity of that element
relate mole and molecule
the mole describes the number of molecules in a substance
how many molecules are in any molecular compound?
6.02 x 10 23
1 mole of H2 contains how many molecules?
6.02 x 10 23 h2 molecules
how can you determine the number of moles of atoms in a mole of molecules by doing what?
looking at the subscripts
what other thing can a mole describe?
the number of ions in an ionic compound
if a substance is an ionic compound how is it represented?
one mole of an ionic compound contains how many formula units does it contain
6.02 x 10 23 formula units
what do ionic compounds look like?
three dimensional crystals with cations and anions
what is the formula unit?
the lowest whole number ratio of elements in an ionic compounds
the number of items in a mole of a substance is ___, mass of the mole ___
what does the molar mass depend on?
particles, atoms, molecules or formula units that make up a substance
what is the atomic mass and molar mass of calcium?
40 amu; 40g/mole
what is the formula mass and molar mass of C6H12O6
fm- 180 amu mm- 180 g/mole
why is the mole the central unit in converting them amount of a substance from one measurement to another?
because a mole measures a mass, number of particles, volume of gas
if you know the number of moles in a substance how many particles are there?
6.02 x 10 23 times that number of moles
how do you find out how many molecules are in 2 moles of water
mutiply the n umber of molecules in one mole of water by 2.
what did avagadro say about gases?
at the same temperature and pressure, equal volumes of gas contain the same number of gas particles
the molar volume relationship can be used to convert between what?
the volume of that gas at STP, PRESSURE, NUMBER OF MOLES OF GAS
what is the percentage composition of compound? how do you find it?
it is the percentage by mass of each element in the compound. it is determined by dividing the mass of each element by the mass of the entire compound and multiplying by 100%
what is the empirical formula?
simplest whole number ratio of atoms of elements in a compound
How can you find the empirical formula?
using the mass of each element and calculating the moles of each element then comparing mole ratios
how can the empirical formula ALSO be calculated?
caculated from the percentage composition of the compound
what is the molecular formula?
gives the actual number of atoms of each element in a molecular compound.
how can the molecular formula be calculated?
diving the molar mass of the compound by the empirical formula mass
relate moles and atoms
atoms are the "mole" of particles in an element
relate moles and molecules
a mole describes the number of molecules in a substance
what particles are you describing when you say a mole of hydrogen?
hydrogen atoms or hydrogen molecules because it is diatomic
a mole can describe the number of ___ in an ionic compound
1 mole of sodium chloride contains what?
6.02 x 10 23 formula units of NacL
formula units can be described in terms of what?
For each of the following substances list the representative particle, number of particles in 1 mole, and the mass of one mole
1. Neon 2. Oxygen 3. Water 4. Magnesium Oxide
1. atom, a.n, 20.2 g 2. molecule, a.n, 32 g 3. molecule, a.n,18 g 4. formula unit, a.m, 40.3 g
what is the molar mass?
the mass in grams of 1 mole of a substance
what does the molar mass depend on?
the masses of the different particles
how can you determine the molar mass?
looking at the atomic mass or formula mass
how can formula mass and molar mass be expressed?
formula mass = amu molar mass = g/mole
why is the mole the central unit in converting a substance from one measurement to another?
because the mole measures both a mass and a number of particles
you have a sample of sodium chloride with a mass of 11.2 grams, how many moles of sodium chloride are in this?
-1 mole of NaCl has a mass of 58.5 grams - 112 g NaCl x 1 mole NaCl --------------- 58.5 g NaCl
= .191 mole of NaCl
how many molecules are in 2 moles of water?
(6.02 x 10 23) x 2 = 12.0 x 10 23
what did avagadro propose about gases?
he said that at the same temperature and pressure, equal volumes of gases contain the same number of gas particles
the volume of a gas is known as what?
molar volume because it is the volume of one mole of gas at standard conditions
the value of 22.4 L/mole of gas only applies to what?
to gases at standard temperature and pressure
the formula for a compound indicates what?
the number and kind of each atom in a representative particle of the compound
what is the mass of a compound made up of?
made up of smaller amounts of different elements
what is the percentage composition of a compound?
the mass of each element in a compound compared to the entire mass of the compound and multiplied by 100
what are the two ways in which you can find percent composition?
1. from the given formula, you take the amount of each element, divide by its atomic mass then times 100 2. experimental analysis.
a sample of an unknown compound with a mass of 0.2370g is extracted from the roots of a plant. decomposition of the sample produces 0.09480 g of C, 0.1264 g of O, and 0.0158 g of H. what is the percent composition of the problem?
-Determine the percentage of each element in the compound
C= 0.0948g/ 0.2370g x 100% = 40%
O= 0.1264g/0.2370g x 100% = 53.3%
H= 0.0158g/0.2370g x 100% = 6.67%
the ratio of atoms will be what?
the ratio of atoms will be the simplest whole number ratio of atoms of the elements in a compound
a formula that gives the simplest whole number ratio of the atoms of the elements
what do subscripts in a compound indicate?
the number of moles of atoms
a compound was analyzed and found to contain 13.5 g of Ca, 10.8 G of O, and 0.675 g of H. what is the empirical formula for the compound?
- convert the mass of each element to the number of moles using molar mass
13.5 g Ca x 1 mol / 40.08 g = 0.337 mol Ca
10.8g O x 1 mole O/ 16.0 g O = 0.675 mol O
0.675g H x 1 mol H/ 1.01g H = 0.668 mol H
- divide each by the smallest number of moles
0.337mol Ca/0.337 = 1 mole of Ca 0.675 mol O/0.337 = 2.00 mol O 0.668 mole H/ 0.337= 1.98 mol H
the mole ratio of the elements is ..
1Ca: 2O: 2H so.. the empirical formula is CaO2H2
what does the empirical formula of a compound indicate? what doesnt it tell?
the simplest ratio of atoms in the compound, but it doesnt tell the actual number of atoms in each molecules
the exact number of atoms in each molecule of a compound determines what?
determines the properties, or characteristics of that compound
the formula that gives the actual number of atoms of each element
ribose has a molar mass of 150g/mole and a chemical composition of 40.0% C, 6.67% H, and 53.3% O. what is the molecular formula for ribose?
1. find the empirical formula
40%C: 40g x 1 mol C/ 12 g C = 3.33 moles of Carbon
6.67% H: 6.67g x 1 mol H/ 1 g H = 6.60 moles of Hydrogen
53.3%O: 53.3g x 1 mol O/16g = 3.33 moles of Oxygen