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Thermochem
Thermochem
MCQ
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100

This is the study of energy changes that occur during chemical and physical changes.

Thermochemistry

100

A sample of peanut is combusted directly below a can containing 250.0 g of water initially at 24.0 degrees Celsius. The reaction releases 4.2 kJ of heat energy, all of which is transferred to the water. What is the final temperature of the water? (The specific heat of water is 4.2 J/(gxC).)

28.0 degrees Celsius



100

Hydrogen peroxide, which is often used to disinfect tools and clean surfaces, can decompose to water and oxygen by the reaction below. Is the reaction endothermic or exothermic? Calculate the quantity of heat released when 5.00 g of liquid hydrogen peroxide decomposes at constant pressure.


exothermic

-14.4 kJ

or

14.4 kJ are released

100

Ice melting to form liquid water is an example of

a. An exothermic process because it releases heat

b. An endothermic process because it releases heat

c. An exothermic process because it absorbs heat

d. An endothermic process because it absorbs heat

d. An endothermic process because it absorbs heat

100

Riddle: I can be cracked. And I can be made. I can be told. And I can be played. What am I?

a joke

200

The ______ of a substance is the amount of heat needed to raise the temperature of 1 gram of the substance by 1 degree Celsius

specific heat capacity

200

When 27.0 g of an unknown metal at 88.4 °C is placed in 115 g H2O at 21.0°C, the final temperature of the water is 23.7°C. What is the specific heat capacity of the metal? The specific heat capacity of water is 4.184 J/g·K.

0.740 J/g·K

200

The gas-phase decomposition of iodoethane, C2H5I(g), is represented above. The bond enthalpies for the bonds broken and formed in the reaction are shown below. Determine the enthalpy of the decomposition reaction. 


87 kJ/mol

200

2Ca(s) + O2(g) --> 2CaO(s)      ΔH = x

Ca(s) + CO2(g) + 1/2O2(g) --> CaCO3(s)     ΔH = y

Based on the information in the table below, which of the following expressions is equal to ΔH rxn for the reaction represented below?

CaCO3(s) --> CaO(s) + CO2(g)

a.)  x/2 + y

b.)  x/2 - y

c.)  x + 2y

d.)  x - 2y

b.)  x/2 - y

200

What is a group of owls called? 

a. an army

b. a bewilderment

c. a parliament

d. a surprise

c. a parliament


300

What is shown in the diagram below?


coffee cup calorimeter

300

C2H5OH(l) + 3O2(g) --> 2CO2(g) + 3H2O(l) 

Enthalpy of reaction = -1367 kJ/molrxn


Ethanol, C2H5OH(l) (molar mass 46.1 g/mol), has been proposed as an alternative to traditional cooking fuels. The combustion of C2H5OH(l) is represented by the equation above. Calculate the mass of C2H5OH(l) that would need to be combusted to heat 250.0 g of water from 20.0 degrees Celsius to 100.0 degrees Celsius. (Assume that all of the heat released by the reaction is absorbed by the water and that the specific heat of water is 4.18 J/(gxC).)

2.82 g

300

The bond enthalpies of the N≡N and F-F bonds are 945 kJ/mol and 159 kJ/mol, respectively. Based on the value of 𝛥Hrxn for the reaction represented below, what is the average bond enthalpy (in kJ/mol) of a N-F bond in NF3?


N2(g) + 3 F2 → 2NF3(g)   𝛥Hrxn = -264 kJ/mol

281 kJ/mol

300

Cl2(g) + F2(g) --> 2ClF(g)

Based on the bond enthalpies given in the table below, what is the value of ΔH rxn for the reaction above?

a. -140 kJ/mol

b. -120 kJ/mol

c. 120 kJ/mol

d. 140 kJ/mol

b. -120 kJ/mol

300

Which two mammals lay eggs?

The echidna and the platypus.


400

The heat absorbed or released from a system under constant pressure is known as this.

Enthalpy

400

A student mixes 50.0 mL of 1.0 M HCl(aq) and 50.0 mL of 1.0 M NaOH(aq), both at 21.0°C, in a coffee-cup calorimeter. The temperature of the resultant solution increases from 21.0°C to 27.5°C. The products are liquid water and aqueous sodium chloride. Calculate the enthalpy change for the reaction in kJ/mol HCl, assuming that the calorimeter loses only a negligible (so small or unimportant as to be not worth considering) quantity of heat, tha the total volume of the solution is 100.0 mL, that its density is 1.0 g/mL, and that its specific heat is 4.18 J/(g°C).

-54 kJ/mol HCl

400

Solve for the enthalpy of reaction below. 


-304.1 kJ

400

A 15.0 g silver block is heated to a temperature T1 and then dropped into 15.0 g of water at a lower temperature Tin a polystyrene cup. Which of the following is true of the final temperature of the system when thermal equilibrium is reached?

a. The final temperature is closer to T1 than to T2

b. The final temperature is exactly halfway between T1 and T2

c. The final temperature is closer to T2 than to T1

d. The final temperature cannot be determined without knowing T1 and T2

c. The final temperature is closer to T2 than to T1

400

What city is famous because it was destroyed in 79 AD when a nearby volcano, Mount Vesuvius, erupted, covering it in at least 6 meters of ash and other volcanic debris?

Pompeii


500

This states the total enthalpy change during the complete course of a chemical reaction is independent of the sequence of steps taken.

Hess's Law


500

When aqueous lead (II) nitrate and aqueous sodium sulfide react, solid lead (II) sulfide and aqueous sodium nitrate are formed. When a 50.0 mL sample of 0.20 M aqueous lead (II) nitrate and a 50.0 mL sample of 0.20 M aqueous sodium sulfide are mixed in a calorimeter, a reaction occurs. If the temperature of the mixture increases from 23.0C to 26.0C, what is the experimental value of ΔH rxn in kJ/mol Pb(NO3)2?

-130 kJ/mol

500

Provide a real world example of technology that takes advantage of water's high specific heat capacity. 

Ex - water can be used to harness the Sun’s energy. Solar radiation beats water, which is circulated in buildings to provide heat. 

500

Name the song.

Dance Monkey