Heat and Stoichiometry Flashcards
True or False: heat is an intrinsic component of physical and chemical changes.
True
When heat must be added, meaning that the reaction requires energy, what is this process referred to as?
An endothermic reaction
Do physical and chemical changes involve energy changes as well?
Yes
When heat is lost, meaning that the reaction is releasing energy, what is this process referred to as?
An exothermic reaction
Energy can be released in what forms?
Sound, light, and heat
What is the reverse chemical reaction to combustion?
Electrolysis of liquid water to form hydrogen and oxygen
True or False: Energy can be viewed as either a reactant or a product in a chemical reaction
True
The amount of energy scales with what?
The amount of reactants used or products made
What is the definition of an endothermic reaction?
a reaction in which energy is absorbed from the surroundings
What is the definition of an exothermic reaction?
a reaction in which energy is released to the surroundings
When water is boiled and evaporated, heat must be added to the liquid water to form gaseous water this is a process of?
Endothermic reaction
When liquid water freezes to form ice, heat is lost during this process which makes this an example of?
Exothermic reactions
What is the SI unit of energy?
Joules (J)
True or False: Joules can be scaled up to kilojoules (kJ) just as we scale grams up to kilograms
True
What do we use joules and kilojoules for in a chemical reaction?
We use joules and kilojoules to quantify the energy involved in a chemical reaction similar to how we use moles and grams to quantify the reactants and products in a chemical reaction
When a reaction mixture’s temperature rises, this indicates?
An exothermic reaction because heat is the byproduct as the temperature is rising
When a reaction mixture’s temperature drops, this indicates?
An endothermic reaction because heat is being absorbed which will not make it a product
Which of the following are examples of endothermic reactions/processes?
A. Solid ammonium nitrate is added to a beaker of water. As it dissolves, the beaker feels cold.
B. When hydrogen gas and oxygen gas react to form water, a burst of flames is observed.
C. Solid sodium hydroxide pellets are added to a beaker of water. The beaker begins to feel warm to the touch.
D. Water is brought to a boil by placing a beaker of water onto a hot plate.
A- Heat is being absorbed meaning the energy will not be a product, therefore it will be a reactant
D- the water is boiling because it is absorbing the heat from the hot plate
Which of the following are examples of exothermic reactions/processes?
A. Solid ammonium nitrate is added to a beaker of water. As it dissolves, the beaker feels cold.
B. When hydrogen gas and oxygen gas react to form water, a burst of flames is observed.
C. Solid sodium hydroxide pellets are added to a beaker of water. The beaker begins to feel warm to the touch.
D. Water is brought to a boil by placing a beaker of water onto a hot plate.
B- energy is being produced explicitly
C- The product of the beaker is heat after the pellets were added
A reaction releasing or absorbing energy is the result of chemical bonds being broken and formed. As such, if one chemical bond being formed releases y amount of energy, how much energy would be released if 100 of these bonds were formed?
100y
Using the following information, determine the amount of energy released when 0.835 g hydrogen gas is ignited in the presence of excess oxygen.
2 H2 (g) + O2 (g) → 2 H2O(g) + 483.6 kJ
- kJ
