HESS LAW

Question 1

A chemical equation that includes the entalphy change (∆H) of the reaction.

• ∆ (final - initial) = entalphy

Answer 1

Thermochemical equation

Question 2

Represents the heat absorbed or released during the reaction at constant pressure

Answer 2

Entalphy change

Question 3

• ___ When we say absorbed
•___ when we say released

Answer 3

Endothermic
Exothermic

Question 4

A chemical equation that gives us information about the state of reactants and products and the energy changes that accompany a chemical reaction

Answer 4

Thermochemical equation

Question 5

∆H rxn =

Answer 5

• 285.8 kJ

Question 6

CH4 - methane
202 - 2 moles of oxygen gas
CO2 - 1 mole of carbon dioxide
2H20- 2 moles of water

Question 7

CH4+ 202 —> CO2 + 2H20
• CH4 +202 —> CO2 + 2H20+ ∆H

Question 8

When a reaction ___ energy, it is ___. This means that the reaction releases heat to its sorroundings.
Ex: The combustion methane (CH4) liberates energy and is an exothermic reaction

Answer 8

Liberates
Exothermic

Question 9

A reaction that absorb energy from their sorroundings.

Ex: The process of photosynthesis in plants, where energy from sunlight is absorbed to convert carbon dioxide and water into glucose and oxygen

Answer 9

Endothermic

Question 10

Pioneer of hess law

Answer 10

German hess

Question 11

Based on the idea that energy is conserved and cannot be created or destroyed.

Answer 11

Hess law

Question 12

The entalphy change of a chemical reaction is independent of the path taken

Answer 12

Hess law

Question 13

It states that the total entalphy change of a reaction is the same, no matter how many steps the reaction is carried out in. In other words, if you can add up the entalphy change of individual steps to get the overall entalphy change, the path taken doesn’t matter

Answer 13

Hess law

Question 14

What formation is this in hess law?

C+ 02 —> CO2 ∆H= -393.5 kJ

• kahit anong gamitin ito parin ang makukuha

Answer 14

Direct formation

Question 15

What type of formation is this in hess law?

C+ ½O2—> CO2 ∆H= -110.5 kJ
Formation of carbon monoxide (CO)

• kalahati lang ang gagamitin

Answer 15

Two step formation

Question 16

HESS LAW
Step 1: when re-writing the value (-) change into (+)
Step 2: 2CO2 (g) becomes 2C(s) + 202 (g) —> 2CO2 (g)
Step 3: H2O becomed H2(g) + 1/2 O2 (g) —> H20
Step 4:

Answer 16

Flip reactants to product (product ang mauuna)
Multiple by two the first product
Do nothing to second product
Add up ∆H