Chemistry Chapter 10 Chemical Quantities

What is the molar volume of a gas at standard temperature and pressure (STP)?

22.4L

What is the molar mass of KI (potassium iodide)?

39.1gK + 126.9GI= 166.0gKI

Look at Figure 10.16 and Table 10.3. Name three compounds that have empirical formula of CH

Ethyne, styrene, benzene.

How many gas particles occupy a volume of 22.4 L at standard temperature and pressure?

6.02 x 10^23 particles

SO3= 1 S atom + 3 O atoms

80.1 amu= 32.1 amu +48.0 amu

The Mole

A formula such as CaCl2 can represent either: -One Ca2+ ion and two Cl- ions or -A mole of Ca2+ ions and two moles of Cl- ions. A mole is a collection of 6.02 x 10^23 particles. There is exactly 1 mole of atoms in the atomic mass of an element when that mass is expressed in grams.

In the diagram below, which compound has a greater percent composition of chromium?

Potassium Dichromatic

How do you determine the mass of a mole of a compound?

The mass of a mole of a compound is determined by adding the atomic masses of the atoms making up the molecule.

Molar mass

The molar mass is the mass in grams of one mole of a substance. Example, one mole of carbon atoms has a molar mass of 12.0g. The molar mass for an element is the same as its average atomic mass. The molar mass of a compound can be calculated from the molar masses of the elements. You must add the individual molar masses of all the atoms shown in the formula.

An empirical formula of a compound gives the

lowest whole-number ratio of the atoms of the elements in a compound.

To calculate the percent composition of a know compound start with the chemical formula of the compound and calculate the

molar mass, which gives the mass of one mole of the compound.

Is the following sentence true or false? The empirical formula of a compound is always the same as the molecular formula

False

Is the following sentence true or false? The volumes of one mole of different solid and liquid substance are the same.

False

Is the following sentence true or false? To determine the number of representative particles in a compound, you count the molecules by viewing them under a microscope.

False.

Examples of the Mole

For example, the atomic mass of carbon is 12. 0 amu. At the same time, 1 mole, or 6.02 x 10^23, is the number of particles in a mole.

Representative particle for Molecular compounds

Formula Unit

What is the letter of the term that is NOT a representative particle of a substance?

Grain

What units do you normally use to describe the density of a gas?

Grams per liter (g/L)

What is the molar mass of a substance?

It is the mass (in grams) of one mole of the substance.

What is the molar mass of a compound?

It is the mass of 1 mol of that compound.

Percentage Composition

Mass of element in compound/total mass of compound x 100%

What is the formula for the percent by mass of an element in a compound?

% mass of elements. Grams ofe/Grams ofc X 100%

What is the temperature that is defined as standard temperature?

0 degrees Celcius

Look at Figure 10.9 on page 300 to help you answer this question. Why is Avogadro's hypothesis reasonable?

As long as the gas particles are not tightly packed, there is a great ideal of empty space between them. A container can easily accommodate the same number of relatively large or relatively small gas particles.

Elements

Atoms

Example of Percentage Compsition

Copper(I) sulfide is found in nature as the mineral chalcocite, a copper ore. What is the percent composition of pure chalcocite? Determine the formula-> Cu2S Determine the molar mass for Cu2S: Cu molar mass: 2 x 63.5= 127.0g/mol S molar mass: 1 x 32.1= 32.1g/mol. Add those together and the Cu2S molar mass would be 159.1g/molUse the molar masses of Cu and S to set up calculation of percentage composition for each element in the compound. Percentage Cu= 127.0 g Cu/ 159.1 g Cu2S x 100%= 79.87% Cu Percentage S= 32.1 g S/ 159.1 g Cu2S x 100%= 20.2% S.

List two or three ways to measure matter.

Count the matter, measure the mass or weight, measure the volume.

What is the term of an SI unit for measuring the amount of a substance?

Mole.

Representative particle for ionic compounds

Molecule

How do you calculate the grams of an element in a specific amount of a compound?

Multiply the mass of the compound by a conversion factor that is based on the percent composition.

How do you express relative amounts of each element in a compound?

Relative amounts are expressed by the percent composition or the percent by mass.

Sodium chloride

Representative Particle: Formula Unit Chemical Formula: NaCl Representative Particles in 1.00 mole: 6.02 x 10^23

Atomic Oxygen

Representative particle: Atom Chemical Formula: O Representative Particles in 1.00 mol: 6.02 x 10^23

Sodium ion

Representative particle: Ion Chemical Formula: Na+ Representative Particles in 1.00 mole: 6.02 x 10^23

Oxygen Gas

Representative particle: Molecule Chemical Formula: O2 Representative particles in 1.00 mol: 6.02 x 10^23

What is Avogadro's Hypothesis?

Says that equal volume of gases at the same temperature and pressure contain equal number of particles.

The volume of a gas varies with a change in

Temperature, the size of the container, and pressure.

What is the atomic mass of an element?

The atomic mass of an element is the mass of a single atom in atomic mass units.

What is Avogadro's number?

The quantity of atoms/molecules in one mole of any substance.

What do the questions "how much?" and "how many?" have in common?

They are questions about the amount of a substance and are similar to questions scientists ask.

Is the following sentence true or false? Molar masses can be calculated directly from atomic masses expressed in grams.

True

Is the following sentence true or false? Stand pressure is 101.3 kPA or 1 atmosphere (atm).

True

Is the following sentence true or false? You can use percent composition to calculate the number of grams of an element in a given amount of a compound.

True

How can you determine the number of atoms in a mole of a molecular compound?

Use the chemical formula to find the number of atoms in one molecule and multiply the number by Avogadro's number, the number of particles in one mole.

Another example of Molar mass would be

What is the molar mass of barium nitrate? Ba(NO3)2 Every mole of the compound contains 1 mole of Ba, 2 moles of N, and 6 moles of O. Ba molar mass: 1 x 137= 137g/mol N molar mass: 2 x 14.0= 28.0g/mol O molar mass: 6 x 16.0= 96.0g/mol. add those together and the Ba(NO3)2 molar mass would be: 261 g/mol.

Example of Molar Mass

What is the molar mass of sodium chloride? (NaCl) Every mole of the compound contains 1 mole of Na and 1 mole of Cl Na molar mass: 23.0g/mole Cl molar mass: 35.5g/mole. add those together and the NaCl molar mass would be 58.5g/mole.

Another Example of Percent Composition

You may determine the last percentage by subtracting the total percent from 100j. 100%-79.87= 20.13% Knowing a compound's percent composition is the first step in determining the formula of that compound. A compound analyzed in a chemistry lab consists of 5.34 g of carbon, 0.42 g of Hydrogen, and 47.08 of Chlorine. What is the percent composition of this compound? Mass of compound= mass of C + mass of H + mass of Cl= 5.34g + 0.42g + 47.08 g= 52.84g The percent of each element in the compound is calculated as follows: Mass of the element/ total mass of the compound x100% Percent C= 5.34g C/ 52.84 g cpd x100%= 10.1% Percent H= 0.42 g H/ 52.84 cpd x 100%= 0.79% Percent Cl= 7.08 g Cl/ 52.84 cpd x 100%= 89.10%

The atomic masses of all elements

are based on the mass of the carbon isotope C-12.

The number of percent values in the percent composition of a compound is

as many as there are different elements in the compound.