Chemistry 30 Thermochem Review

Refer the the following question:
2N₂ + 3H₂ --> 2NH₃ + 46 kJ
How much energy would be produced if only 1 mol of nitrogen was reacted?

• 92 kJ
• 0.143 kJ
• 23 kJ
• 15 kJ

How much energy must be used to produce 4.75 mol of gaseous water?

H₂O (l) + 44.0 kJ --> H₂O (g)

• 209 kJ

• 9.26 kJ

• 206 kJ

• 9.36 kJ

In a laboratory experiment a student was using Styrofoam cups and foil to reduce the energy lost during an exothermic reaction.  The reaction constantly had a temperature probe in it.  Towards the end of the reaction the student noticed the temperature in the cups was going down (opposite what they thought is should).  The student concluded that the energy was destroyed within the system.  This student's reasoning violates what law?

• Law of Conservation of Mass
• Law of Enthalpy
• First Law of Thermodynamics
• Law of Heat Transfer

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

The potential energy diagram of a reaction is shown. Which statement below is correct relating to this reaction?

• #1 represents the enthalpy change for this exothermic reaction.

• #2 represents the enthalpy change for this endothermic reaction.

• #3 represents the enthalpy change for this endothermic reaction.

• #4 represents the enthalpy change for this exothermic reaction.

Tags

NGSS.HS-PS1-4

The amount of heat energy required to change the temperature of 12 g of gold from 45°C to 15°C is -47 J. What is the specific heat capacity of gold?

• 0.13 J/(g°C)

• 17,000 J/(g°C)

• 1600 J/(g°C)

• 0.065 J/(g°C)

Tags

NGSS.HS-PS3-4

When methane, CH4, and oxygen, O2, are mixed in a stove and ignited, a lovely blue flame results. The balanced equation is: CH₄(g) + 2O₂(g) 2H₂O(g) + CO₂(g) What can be said about the energy involved in this chemical reaction?

I. The average kinetic energy of the products is greater than that of the reactants.

II. The chemical energy stored in the reactants is greater than the chemical energy stored in the products.

III. Chemical energy in the reactants is changed into heat energy and light energy.

• I only

• II only

• III only

• I, II, and III

Tags

NGSS.HS-PS1-4

If 100 g of aluminum at 145ºC gains 6,800 J of heat, what is the final temperature (T_final) of the aluminum? Aluminum has a specific heat of 0.897 J/gºC. (Q=mcΔT)

• -69°C
• 0.52°C
• 221°C

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

The diagram represents which type of reaction

• endothermic
• exothermic

Tags

NGSS.HS-PS1-4

How do you calculate Enthalpy of a reaction?

• ΔH = ΔH_products - ΔH_reactants

• ΔT = q / mC

• ΔG = ΔH -TΔS

• E = mc²

Tags

NGSS.HS-PS1-4

What is standard enthalpy of formation, ΔH_f^o?

• Heat change when 1 mole of gaseous ions is hydrated in water at 25^oC and 1 atm

• Heat change when 1 mole of compound is formed from its elements in their standard states at 25^oC and 1 atm

• Heat change when 1 mole of gaseous atom is formed from its elements at 25^oC and 1 atm

• Heat change when 1 mole of electrons is removed from 1 mole of gaseous atoms at ground state at 25^oC and 1 atm