4.13 Unit Test: Chemical Thermodynamics

A chemical reaction is carried out in a closed container. The energy absorbed by the chemical reaction is 200 kJ. What is the energy liberated from the air or the walls of the container?

200 kJ

Which statement is true? In an endothermic reaction, the energy of the products is the same as the energy of the reactants. In an exothermic reaction, the energy of the products is less than the energy of the reactants. In an endothermic reaction, the energy of the products is less than the energy of the reactants. In an exothermic reaction, the energy of the products is the same as the energy of the reactants.

2nd one In an exothermic reaction, the energy of the products is less than the energy of the reactants.

In a calorimeter, 100 g of ice melts at 0oC. The enthalpy of fusion of the ice is 334 J/g. How much heat was absorbed?

33.4 kJ Remember the answer is 33.4 kJ, it's not 33.4 J. I got mine wrong originally because of that mistake.

How much heat do you need to raise the temperature of 150 g of ice from −30 °C to −15 °C ?

4.61 kJ

Which statement is a correctly written thermochemical equation?

4Fe (s) + 3O2 (g)→2Fe2O3 (s), ΔH = −3,926 kJ

In a calorimeter, 20 g of ice absorbs heat with an enthalpy of fusion of 334 J/g. What is the heat absorbed? q=mΔHf

6.68 kJ

In which thermochemical equations would the ΔH be considered a heat of solution?

NH4NO3(s)→NH4+(aq)+NO3-(aq), ΔH=+25.7 kJ/mol

Which example is an exothermic reaction?

condensation

This diagram would represent the enthalpy changes in which example? https://static.k12.com/nextgen_media/assets/1107846-3833175_VHS_CHEM_S2_04_15_102_reactants_products.gif Copy and paste the link above to see the image.

hot pack

Two hundred grams of a substance requires 1.84 kJ of heat to raise its temperature from 25°C to 45°C. Use the table to identify the substance. q=mCΔT. Mass (m) is in grams. Temperature is in degrees Celsius.

iron

Which parameter is measured directly in a coffee-cup calorimeter?

temperature

Which term measures thermal energy in an object?

temperature

You have a series of four chemical reactions (1→2→3→4). How do you calculate the ΔH2 if you know the other ΔH values?

ΔH2=ΔH4−(ΔH1 + ΔH3)

What is likely to be true about the ΔH for this reaction? C6H6 (s) → C6H6 (l)

∆H > 0

Consider these equations: 2S (s) + 3O2 (g)→2SO3 (g), ΔH = −792 kJ 2S (s) + 2O2 (g)→2SO2 (g), ΔH = −594kJ 2SO2 (g) + O2 (g)→2SO3 (g), ΔH =? What is the missing ΔH?

−198 kJ

How much heat is given off when 16 g liquid methanol (CH3OH) at its freezing point changes to solid methanol? (methanol ΔHf=3.16 kJ/mol)

1.58 kJ

The reaction 2NO (g) → N2 (g) + O2 (g) has a ΔH =−180.5 kJ . How much heat will be required to produce 44.8 L of NO by the reverse reaction?

180.5 kJ

Two objects (A and B) of the same temperature are in contact with each other. Which statement is true?

Although the molecules collide, no heat transfers because there is no temperature difference between the objects

Which type of substance would be best for use in a cooling system?

a liquid with a high specific heat

What is the change in enthalpy when 180 g of water vapor condenses at 100oC? (ΔHv=40.67 kJ/mol)

−407 kJ Pay close attention its not 407 kJ, it is -407kJ. I didn't and got this one wrong because of that.