Chemical Equations

Question 1

What is the basic “formula” for a chemical reaction?

Answer 1

Reactants—>products

Question 2

Chemical reaction can be abbreviated as…

Answer 2

rxn

Question 3

Chemical…are made up of…representing the…and…

Answer 3

Chemical equations are made up of symbols representing the reactants and products.

Question 4

How do you remember which elements are always diatomic molecules?

Answer 4

HOFBrINCl: Hydrogen, oxygen, fluorine, bromine, iodine, nitrogen, chlorine

Question 5

What is a catalyst?

Answer 5

A substance that speeds up a reaction but is not used up in the reaction.

Question 6

What does this symbol do in a chem equation: +

Answer 6

Separates two or more reactants/products.

Question 7

What does this symbol do in a chem equation: —>

Answer 7

Means “yields/produces,” used to separate reactants from products

Question 8

What does this symbol do in a chem equation: (s)

Answer 8

Indicates a reactant/product in solid state- placed after formula

Question 9

What does this symbol do in a chem equation: (l)

Answer 9

Indicates a reactant/product in liquid state- placed after formula

Question 10

What does this symbol do in a chem equation: (g)

Answer 10

Indicates a reactant/product in gaseous state- placed after formula

Question 11

What does this symbol do in a chem equation: (aq)

Answer 11

Indicates an aqueous solution, substance is dissolved in water; placed after formula

Question 12

What does this symbol do in a chem equation:—-> with “heat” or a triangle on top:

Answer 12

Indicates that heat is applied to the reaction

Question 13

What does this symbol do in a chem equation:—–> with an element symbol (like Pt) on top:

Answer 13

Indicates that the element was used as a catalyst

Question 14

How do you balance an equation?

Answer 14

Place coefficients in front of substances.

Question 15

Can you balance an equation by changing subscripts?

Answer 15

No, because that changes the reactants/products themselves.

Question 16

Why must equations be balanced?

Answer 16

In order to obey the law of conservation of mass.

Question 17

Read the following reaction: Two molecules of water (H2O) produces 1 molecule of oxygen (O2) and 2 molecules of hydrogen (H2). How do you say this using moles?

Answer 17

Two moles water produces 1 mole oxygen and 2 moles hydrogen.

Question 18

Define chemical reaction.

Answer 18

The process by which some substances change into different substances.

Question 19

What happens with atoms and their bonds in a chem reaction?

Answer 19

The types and ratios of atoms stay the same, but the bonds of the reactants break and form new bonds to make the products, therefore rearranging the atoms.

Question 20

What do reactants do?

Answer 20

They start the reactions.

Question 21

What are the products in a reaction?

Answer 21

The end result.

Question 22

What is the basic equation for a synthesis reaction?

Answer 22

A+B—>C

Question 23

What is the basic equation for a decomposition reaction?

Answer 23

AB—>A+B

Question 24

What is the basic equation for a double replacement reaction?

Answer 24

AB+CD—>AD+CB

Question 25

What is the basic equation for a single replacement reaction?

Answer 25

A+BC--->B+AC

Question 26

What is the basic equation for a combustion reaction?

Answer 26

Fuel+oxygen--->carbon dioxide+water

Question 27

All chemical reactions involve...

Answer 27

energy.

Question 28

Why is energy involved in chemical reactions?

Answer 28

It takes energy to break the bonds of the reactants and energy is released when new bonds are formed for th e products.

Question 29

What is an exothermic reaction?

Answer 29

Energy released in the reaction is greater than energy used. The energy is released as light or heat. (Energy released by formation of bonds in products exceeds energy used to break reactants' bonds.)

Question 30

What is an endothermic reaction?

Answer 30

Energy used up in the reaction (to break reactants' bonds) is greater than energy released in the reaction (as products form bonds). Energy is absorbed, not released.

Question 31

What is the energy in an exothermic reaction released as?

Answer 31

Light or heat.

Question 32

When you write a chemical equation from words, and you are dealing with a one-word reactant/product, how do you write its symbol?

Answer 32

One word= element. If it is a HOFBrINCl element, it is diatomic, write as such (N2). If it is not, just write the element symbol (Zn). DO not worry about charges.

Question 33

When writing a chemical equation from words, how do you write a two-word reactant/product?

Answer 33

Two words means it is a compound. If it is ionic, use ion charges. If it is covalent, it is either an acid or a binary covalent. Write the binary covalent with the subscripts that correspond to prefixes, and use reference sheet to write acid formulas (these start with hydrogen).

Question 34

What are two standard "templates" for composition/synthesis reactions?

Answer 34

Element+element--->binary compound | Compound+compound---> new compound

Question 35

Composition/synthesis reactions have how many products?

Answer 35

1

Question 36

What are two standard "templates" for decomposition reactions?

Answer 36

Binary compound---> element + element | Compound--->element + compound

Question 37

How many reactants and products are in decomposition reactions?

Answer 37

1 reactant, and more than one product

Question 38

What is the standard "template" for single replacement reactions?

Answer 38

Element + compound---> new element + new compound

Question 39

What is the standard "template" for double replacement reactions?

Answer 39

Compound+compound---> new compound+ new compound

Question 40

What elements does a hydrocarbon contain?

Answer 40

Hydrogen, carbon, and sometimes oxygen

Question 41

What is the standard template for combustion (of a hydrocarbon)?

Answer 41

Hydrocarbon + oxygen---> carbon dioxide + water