CHAPTER FIVE: CHEMICAL QUANTITIES AND REACTIONS Flashcards by Jeremy Quintrell

In every chemical reaction, the atoms in the reacting substances, called _________ are rearranged to give new substances called ___________.

REACTANTS

PRODUCTS

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In chemistry, particles such as atoms, molecules and ions are counted by the ______, a unit that contains ___________ items. This very large number is called _________ ________.

…counted by the MOLE, a unit that contains 6.02 x 10^23 items.

AVOGADRO’S NUMBER

1 mole of an element= 6.02 x 10^23 atoms of that element (the particular type of particles that make up that compound)

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One mole of a COVALENT COMPOUND contains Avogadro’s number of _______.

One mole of an IONIC COMPOUND contains Avogadro’s number of _______ ________, which are the groups of ions represented by the formula of an ionic compound.

Covalent= MOLECULES

Covalent= FORMULA UNITS

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We can use Avogadro’s number as a conversion factor to convert between the moles of a substance and the ______ ___ __________ it contains.

NUMBER OF PARTICLES

6.02 x 10^23/ 1 mole AND
1 mole/6.02 x 10^23 particles

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In calculations that convert between moles and particles, the number of moles will be a _______ (small or large?) number compared to the very large number of atoms or molecules.

SMALL

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The SUBSCRIPTS in a chemical formula of a compound indicate both the number of ______ of each type of element AND the number of ________ of each element in 1 mole of the compound.

ATOMS

MOLES

Ex: C9H8O4=

9 carbon, 8 hydrogen and 4 oxygen atoms
9 moles of C atoms, 8 moles of H atoms and 4 moles of O atoms

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Using the subscripts from the formula

C9H8O4, state the conversion factors for each of the elements in one mole of aspirin.

9 moles C/1 mole C9H8O4
8 moles H/1 mole C9H8O4
4 moles O/1 mole C9H8O4

1 mole C9H8O4/9 moles C
1 mole C9H8O4/8 moles H
1 mole C9H8O4/4 moles O

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What are the 4 steps to calculating the MOLES of an ELEMENT in a COMPOUND?

State the given and needed quantities
Write a plan to convert moles of compound to moles of an element.
Write equalities and conversion factors using subscripts.
Set up the problem to calculate the moles of an element.

See page 172 for example

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What is the MOLAR MASS for any element?

The quantity in grams that equals the atomic mass of that element.

We count 6.02 x 10^23 atoms of an element when we weight out the number of grams equal to its molar mass.

Ex: if we need 1 mole of carbon atoms, first find the atomic mass of 12.01 on the Periodic Table. Then to obtain 1 mole of carbon atoms, weigh out 12.01 grams of carbon.

Thus, the MOLAR MASS of carbon is found by looking at the atomic mass on the periodic table. See diagram page 173

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How do you determine the MOLAR MASS of a COMPOUND?

obtain the molar mass of each element.
multiply the molar mass of each element by the number of moles (subscript) in the formula
calculate the molar mass by adding the masses of the elements.

NOTE: in this text, round molar mass to the tenths (0.1g) place or use at least 3 significant figures for calculations.

See page 173 for example

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What are the FOUR steps for calculating the moles (or grams) of a substance from grams (or moles)?

State the given and needed quantities.
Write a plan to convert moles to grams (or grams to moles)
Determine the molar mass and write conversion factors.
Set up the problem to convert moles to grams (or grams to moles)

See page 174-175 for example

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A CHEMICAL REACTION always involves ________ _________ because atoms of the reacting substances from new combinations with new properties.

chemical change

Ex: a chemical reaction takes place when a piece of iron (Fe) combines with oxygen (O2) in the air to produce a new substance, rust (Fe2O3), which has a reddish-brown color.

During a chemical change, new properties become visible, which are an indication that a chemical reaction has taken place.

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What is a CHEMICAL EQUATION?

How is a chemical equation written?

it tells us the materials we need and the products that will form in a chemical reaction (like preparing a recipe or building a model airplane)

In a chemical equation, the formulas of the REACTANTS are written on the left of the arrow and the formulas of the PRODUCTS on the right. When there are 2 or more formulas on the same side, they are separated by plus (+) signs. The delta sign (∆) indicates that heat was used to start the reaction.

The arrow means “reacts to form products”.

Generally, each formula in an equation is followed by an abbreviation, in parentheses, that gives the physical state of the substance: solid (s), or gas (g). If a substance is dissolved in water, it is an aqueous (aq) solution.

See page 178 for examples and diagrams

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When a reaction takes place, the bonds between the atoms of the reactants are ________ and new bonds are formed to give the __________. All atoms are ______, which means ______________

broken; products

conserved; atoms cannot be gained, lost or changed into other types of atoms during a chemical reaction.

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Every chemical reaction must be written as a ________ ____________, which shows the same number of atoms for each element in the reactants as well as in the products.

balanced equation

see examples on page 179

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What is a COEFFICIENT and how is it used to balance equations?

In this process, we do NOT change _______, which would alter the chemical identity of a reactant or product.

When we add up the atoms of each element on each side and we find that the equation is NOT BALANCED:

to balance the equation, we place whole numbers called COEFFICIENTS in front of the formulas
the coefficient multiplies all the atoms in the compound.
the number of atoms are the same in the reactants as in the products and the equation is now BALANCED

We do NOT change SUBSCRIPTS

See page 179 for examples

What are the FOUR steps to balancing a CHEMICAL EQUATION?

Write an equation using the correct formulas of the reactants and products.
Count the atoms of each element in the reactants and products.
Use coefficients to balance each element.
Check the final equation to confirm it is balanced.

See page 180 for examples.

What is a COMBINATION REACTION?

In a COMBINATION REACTION, two or more elements or compounds bond to form one product.

Ex: sulfur and oxygen combine to form the product sulfur dioxide

S(s) + O2(g) arrow SO2(g)

What is a REPLACEMENT REACTION?

What is a SINGLE REPLACEMENT REACTION?

What is a DOUBLE REPLACEMENT REACTION?

In a REPLACEMENT REACTION, elements in a compound are replaced by other elements.

In a SINGLE REPLACEMENT REACTION, a reacting element switches place with an element in the other reacting compound. See pages 184-186 for examples and diagrams.

In a DOUBLE REPLACEMENT REACTION, the positive ions in the reacting compounds switch places. See page 186 for examples and diagrams.

What is a COMBUSTION REACTION?

In a COMBUSTION REACTION, a carbon-containing compound, usually a fuel, burns in oxygen from the air to produce carbon dioxide (CO2), water (H2O) and energy in the form of heat or a flame.

See page 187 for examples and diagrams

What is an OXIDATION-REDUCTION REACTION (redox)?

OXIDATION is defined as _________

REDUCTION is defined as ________

mnemonic- OIL RIG

In an OXIDATION-REDUCTION REACTION (redox), electrons are transferred from one substance to another. If one substance loses electrons, another substance must gain electrons.

OXIDATION is defined as the LOSS of electrons.

REDUCTION is the GAIN of electrons.

OIL RIG (oxidation is loss, reduction is gain)

In general, atoms of metals _____ electrons to form ______ ions….whereas nonmetals _____ electrons to form _________ ions.

Now we can say that _______ are OXIDIZED and ___________ are REDUCED.

Atoms of metals LOSE electrons to form POSITIVE ions…

Atoms of nonmetals GAIN electrons to form NEGATIVE ions…

METALS are oxidized and NONMETALS are reduced.

What is PATINA?

It is the green color that appears on copper surfaces from weathering. It is a mixture of CuCO3 and CuO.

See page 190 for the formula for this.

OXIDATION AND REDUCTION IN BIOLOGICAL SYSTEMS:

Oxidation may also involve the ______ of oxygen or the ____ of hydrogen
Reduction may also involve the ____ of oxygen or the _____ of hydrogen
In the cells of the body, oxidation of organic (carbon) compounds involves the transfer of _________ atoms, which are composed of electrons and protons.

Oxidation- ADDITION of oxygen, LOSS of hydrogen
Reduction- LOSS of oxygen, ADDITION of hydrogen
hydrogen

See page 191-192 for examples

When we do experiments in the lab or prepare meds in the pharmacy, the samples we use contain billions of atoms or molecules, which makes it impossible to count them. What we can measure is their _____, using a ________. Because mass is related to the number of particles through the molar mass, measuring the mass is equivalent to counting __________________________.

MASS; BALANCE ...equivalent to counting the number of particles or moles.

What is the LAW of CONSERVATION OF MASS?

In any chemical reaction, the total amount of matter in the reactants is equal to the total amount of matter in the products. If all the reactants were weighed, they would have total mass equal to the total mass of the products. This is known as the LAW OF CONSERVATION OF MASS, which says that there is no change in the total mass of the substance reacting in a chemical reaction. Thus, no material is lost or gained when original substances are changed to new substances.

What are MOLE-MOLE FACTORS?

When an equation is balanced, we know the proportions of the elements in the reaction. Any amount of the elements may be used, but the RATIO will be the same. From the coefficients, we can write MOLE-MOLE FACTORS between reactants and between reactants and products. The coefficients used in the mole-mole factors are exact numbers; they do not limit the number of significant figures. See page 195 for examples

What are the FOUR steps to using MOLE-MOLE FACTORS?

1. State the given and needed quantities 2. Write a plan to convert the given to the needed moles. 3. Use coefficients to write relationships and mole-mole factors. 4. Set up the problem using the mole-mole factor that cancels given moles. See page 196 for examples

By using MOLE-MOLE FACTORS, you can predict _____________.

...the moles of the product that can be produced.

What are the FOUR steps to calculating the MASSES of REACTANTS and PRODUCTS in a chemical reaction?

1. Use molar mass to convert grams of given to moles (if necessary). 2. Write a mole-mole factor from the coefficients in the equation. 3. Convert moles of given to moles of needed substance using the mole-mole factor. 4. Convert moles of needed substance to grams using molar mass. See page 197-198 for examples.

What are the three conditions required for a REACTION to occur? What is ACTIVATION ENERGY? What is the HEAT OF REACTION?

Three conditions required: 1. COLLISION- the reactants must collide 2. ORIENTATION- the reactants must align properly to break and form bonds 3. ENERGY- the collision must provide the energy of activation. The ACTIVATION ENERGY is the amount of energy required to break the bonds between atoms of the reactants so that product is formed. The HEAT OF REACTION is the difference between the energy of the reactants and the energy of the products (can be exothermic or endothermic reactions)- see next 2 cards

What is an EXOTHERMIC REACTION?

In an EXOTHERMIC REACTION, the energy of the reactants is greater than that of the products. Heat is RELEASED in exothermic reactions.

What is an ENDOTHERMIC REACTION?

In ENDOTHERMIC REACTIONS, the energy of the reactants is lower than that of the products. Heat is ABSORBED in endothermic reactions. See page 200 for examples

How is the RATE (or SPEED) of REACTION measured? Reactions with ______ activation energies go __________ (faster or slower?) than reactions with high activation energies.

It is measured by the amount of reactant used up, or the amount of product formed, in a certain period of time. LOW; FASTER

Reactions almost always go _______ at higher TEMPERATURES. For every 10 degrees Celsius increase in temperature, most reaction rates approximately __________.

FASTER. At higher temperatures, the increase in kinetic energy of the reactants makes them move faster and collide more often, and it provides more collisions with the required energy of activation. DOUBLE

The rate of a reaction __________ when reactants are added.

INCREASES. Then there are more collisions between the reactants and the reaction goes faster.

What is the effect of adding a CATALYST?

Another way to speed up a reaction is to lower the energy of activation. This can be done by adding a catalyst. A catalyst acts by providing an alternate pathway with a lower energy requirement. As a result, more collisions form product successfully.

What is a DECOMPOSITION REACTION?

In a DECOMPOSITION REACTION, a reactant splits into 2 or more simpler products. Ex: when mercury(II) oxide is heated, the compounds breaks apart into mercury atoms and oxygen. See formula on page 184

can't read page 199 to make flashcards about energy in chemical reactions!