Exam 6: Thermochemistry

A 2.38 g sample of phenol (C₆H₆O,molar mass = 94.11 g $\mathrm { mol } ^ { - 1 }$ )was combusted in a bomb calorimeter with a heat capacity of 6.65 kJ ${ } ^ { \circ } \mathrm { C } ^ { - 1 }$ .If the temperature increased from 23.8 °C to 35.4 °C,determine $D _ { \mathrm { r } }$ U for the combustion of phenol.

Use the standard reaction enthalpies given below to determine $D _ { \mathrm { r } }$ H° for the following reaction: 2NO(g)+ O₂(g)? 2NO₂(g) _DrH°= ? Given: N₂(g)+ O₂(g)? 2NO(g) _DrH°= +183 kJ 1/2 N₂(g)+ O₂(g)? NO₂(g) _DrH°= +33 kJ

Hydrogen peroxide decomposes to water and oxygen at constant pressure by the following reaction: $2 \mathrm { H } _ { 2 }$ $\mathrm { O } _ { 2 }$ (l)? $2 \mathrm { H } _ { 2 }$ O(l)+ $\mathrm { O } _ { 2 }$ (g) $\Delta _ { \mathrm { r } }$ H = -196 kJ Calculate the value of q (kJ)in this exothermic reaction when 4.00 g of hydrogen peroxide decomposes at constant pressure?

How much heat is absorbed when 50.00 g of C(s)reacts in the presence of excess SO₂(g)to produce CS₂(l)and CO(g)according to the following chemical equation? 5C(s)+ 2SO₂(g)? CS₂(l)+ 4CO(g) $\Delta _ { \mathrm { r } }$ H° = 239.9 kJ

Calculate the change in internal energy (ΔU)for a system that is absorbing 35.8 kJ of heat and is expanding from 8.00 to 24.0 L in volume at 1.00 bar.(Remember that 100 J = 1 L bar)

A sample of copper absorbs 43.6 kJ of heat,resulting in a temperature rise of 75.0 °C.Determine the mass (in kg)of the copper sample if the specific heat capacity of copper is 0.385 J g^-1 °C^-1.

An unknown metal alloy,mass = 36.1 g,has a temperature change of 31.6 to 24.8 °C after a heat transfer of -103.0 J.Calculate the specific heat capacity of the alloy.

Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter.The reaction causes the temperature of the resulting solution to fall below room temperature.Which of the following statements is TRUE?

The specific heat capacity of solid copper metal is 0.385 J $g ^ { - 1 }$ $\mathrm { K } ^ { - 1 }$ .How many joules of heat are needed to raise the temperature of a 1.55 kg block of copper from 33.0°C to 77.5°C?

An unknown metal alloy,specific heat capacity = 0.613 J g^-1 °C^-1,has a temperature change of 31.02 to 24.77 °C after a heat transfer of -106.4 J.Calculate the mass of the alloy in question.

For a particular process that is carried out at constant pressure,q = 145 kJ and w = -35 kJ.Therefore,

Identify what a coffee cup calorimeter measures.

Determine the specific heat capacity of an alloy that requires 59.3 kJ to raise the temperature of 150.0 g alloy from 298 K to 398 K.

Identify the major greenhouse gas.

Calculate the work,w,gained or lost by the system when a gas expands from 15 L to 40 L against a constant external pressure of 1.5199 bar.

When 2.50 g of Ba(s)is added to 100.00 g of water in a container open to the atmosphere,the reaction shown below occurs and the temperature of the resulting solution rises from 22.00 °C to 40.32 °C.If the specific heat of the solution is 4.18 J $g ^ { - 1 }$ ${ } ^ { \circ } \mathrm { C } ^ { - 1 }$ ,calculate $\Delta H$ for the reaction,as written. Ba(s)+ 2H₂O(l)? Ba(OH)₂(aq)+ H₂(g) $\Delta _ { \mathrm { r } } H$ = ?

Calculate the final temperature of a 63.7 g piece of palladium,originally at 100.0 °C,placed inside a coffee cup calorimeter containing 115.0 mL of water at 21.8 °C.The specific heat capacity of water is 4.184 J g^-1 °C^-1,the specific heat capacity of palladium is 0.246 J g^-1 °C^-1,and the density of water is 1.00 g mL^-1.

Which of the following substances (with specific heat capacity provided)would show the greatest temperature change upon absorbing 100.0 J of heat?

Define molar heat capacity.

Astatine is an extremely rare element with an estimated 28 g total on Earth.How much energy would be required to heat Earth's entire supply of astatine by 10.0 °C assuming it has a specific heat capacity similar to iodine,0.214 J g^-1 °C^-1?