Exam 6: Thermochemistry

The combustion of titanium with oxygen produces titanium dioxide: Ti(s)+ $\mathrm { O } _ { 2 }$ (g)? $\mathrm { TiO } _ { 2 }$ (s) When 2.090 g of titanium is combusted in a bomb calorimeter,the temperature of the calorimeter increases from 25.00 °C to 91.30 °C.In a separate experiment,the heat capacity of the calorimeter is measured to be 9.84 kJ $\mathrm { K } ^ { - 1 }$ .The heat of reaction for the combustion of a mole of Ti in this calorimeter is ________ kJ $\mathrm { mol } ^ { - 1 }$ .

Calculate the internal energy change,Δ_rU,for the combustion of 6.9261 g of diethylene glycol (C₄H₁₀O₃,molar mass = 106.120 g mol^-1)if the combustion inside a bomb calorimeter,C_cal = 13.84 kJ °C^-1,causes a temperature change from 22.8 °C to 34.0 °C.

The specific heat capacity of methane gas is 2.20 J $g ^ { - 1 }$ $\mathrm { K } ^ { - 1 }$ .How many joules of heat are needed to raise the temperature of 5.00 g of methane from 36.0 °C to 75.0 °C?

Using the following equation for the combustion of octane,calculate the amount of moles of oxygen that reacts with 100.0 g of octane.The molar mass of octane is 114.33 g $\mathrm { mol } ^ { - 1 }$ .The molar mass of carbon dioxide is 44.0095 g $\mathrm { mol } ^ { - 1 }$ . 2C₈H₁₈ + 25O₂ ? 16CO₂ + 18H₂O D_rH° = -11018 kJ

Calculate the internal energy change,Δ_rU,for the combustion of 29.3 g of vitamin C (C₆H₈O₆,molar mass = 176.124 g mol^-1)if the combustion inside a bomb calorimeter,C_cal = 8.31 kJ °C^-1,causes a temperature change from 21.5 °C to 68.3 °C.

A 6.55 g sample of aniline (C₆H₅NH₂,molar mass = 93.13 g $\mathrm { mol } ^ { - 1 }$ )was combusted in a bomb calorimeter.If the temperature rose by 32.9 °C,use the information below to determine the heat capacity of the calorimeter. 4C₆H₅NH₂(l)+ 35O₂(g)? 24CO₂(g)+ 14H₂O(g)+ 4NO₂(g) D_rU= -3.20 × 10³ kJ mol^-1

Define chemical energy.

The specific heat of copper is 0.385 J $g ^ { - 1 }$ $\mathrm { K } ^ { - 1 }$ .If 34.2 g of copper,initially at 21.0 °C,absorbs 4.689 kJ,what will be the final temperature of the copper?

An unknown metal alloy,specific heat capacity = 0.372 J g^-1 °C^-1,has a temperature change of +21.7 °C after a heat transfer of 216.4 J.Calculate the mass of the alloy in question.

Which of the following signs on q and w represent a system that is doing work on the surroundings as well as gaining heat from the surroundings?

According to the following reaction,how much energy is evolved during the reaction of 32.5 g B₂H₆ and 72.5 g Cl₂? The molar mass of B₂H₆ is 27.67 g $\mathrm { mol } ^ { - 1 }$ . B₂H₆(g)+ 6Cl₂(g)? 2BCl₃(g)+ 6HCl(g) D_rH° = -1396 kJ

Which of the following statements is TRUE?

A piece of iron (mass = 25.0 g)at 398 K is placed in a styrofoam coffee cup containing 25.0 mL of water at 298 K.Assuming that no heat is lost to the cup or the surroundings,what will the final temperature of the water be? The specific heat capacity of iron = 0.449 J $g ^ { - 1 }$ °C^-1 and water = 4.184 J $g ^ { - 1 }$ °C^-1.

The specific heat capacity of liquid mercury is 0.14 J $g ^ { - 1 }$ $\mathrm { K } ^ { - 1 }$ .How many joules of heat are needed to raise the temperature of 4.00 g of mercury from 19.0°C to 39.5°C?

A 100.0 mL sample of 0.300 mol L^-1 NaOH is mixed with a 100.0 mL sample of 0.300 mol L^-1 HNO₃ in a coffee cup calorimeter.If both solutions were initially at 35.00 °C and the temperature of the resulting solution was recorded as 37.00 °C,determine the $D _ { \mathrm { r } }$ H° (in units of kJ $\mathrm { mol } ^ { - 1 }$ )for the neutralization reaction between aqueous NaOH and HNO₃ .Assume 1)that no heat is lost to the calorimeter or the surroundings,and 2)that the density and the heat capacity of the resulting solution are the same as water.

Calculate the final temperature of 82.1 g of molecular hydrogen (specific heat capacity = 14.304 J g^-1 °C^-1)initially at 5.48 °C that absorbs 57 kJ of energy from the surroundings.

Two solutions,initially at 24.69 °C,are mixed in a coffee cup calorimeter (C_cal = 105.5 J °C^-1).When a 200.0 mL volume of 0.100 mol L^-1 AgNO₃ solution is mixed with a 100.0 mL sample of 0.100 mol L^-1 NaCl solution,the temperature in the calorimeter rises to 25.16 °C.Determine the $D _ { \mathrm { r } }$ H°,in units of kJ $\mathrm { mol } ^ { - 1 }$ .Assume that the density and heat capacity of the solutions is the same as that of water. Hint: Write a balanced reaction for the process.

Explain the difference between ΔH and ΔU.

A balloon is inflated from 0.0100 L to 0.500 L against an external pressure of 10.00 bar.How much work is done in joules? (100 J = 1 L bar)

A piece of iron (C = 0.449 J g^-1 °C^-1 and a piece of gold (C = 0.128 J g^-1 °C^-1)have identical masses.If the iron has an initial temperature of 498 K and the gold has an initial temperature of 298 K,which of the following statements is TRUE of the outcome when the two metals are placed in contact with one another? Assume no heat is lost to the surroundings.