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Exam 10: Thermochemistry

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Question 61

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A 12.8 g sample of ethanol (C₂H₅OH) is burned in a bomb calorimeter with a heat capacity of 5.65 kJ/°C.Using the information below,determine the final temperature of the calorimeter if the initial temperature is 25.0°C.The molar mass of ethanol is 46.07 g/mol. C₂H₅OH(l) + 3 O₂(g) → 2 CO₂(g) + 3 H₂O(g) ΔH°_rxn = -1235 kJ

A) 53.4°C
B) 28.1°C
C) 111°C
D) 85.7°C
E) 74.2°C

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Question 62

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The specific heat capacity of solid copper metal is 0.385 J/gK.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?

A) 1.79 × J
B) 26.6 J
C) 2.66 × J
D) 5.58 × J
E) 0.00558 J

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Question 63

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Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K.The specific heat capacity of ethanol is 2.42 J/g°C.

A 4.98 g sample of aniline (C₆H₅NH₂,molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C.If the temperature rose from 29.5°C to 69.8°C,determine the value of ΔH°_comb for aniline.

When 50.0 mL of 0.400 M Ca(NO₃) ₂ is added to 50.0 mL of 0.800 M NaF,CaF₂ precipitates,as shown in the net ionic equation below.The initial temperature of both solutions is 22.00°C.Assuming that the reaction goes to completion,and that the resulting solution has a mass of 100.00 g and a specific heat of 4.18 J/(g ∙ °C) ,calculate the final temperature of the solution. Ca²⁺(aq) + 2 F^-(aq) → CaF₂(s) ΔH° = -11.5 kJ

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?

Which of the following (with specific heat capacity provided) would show the smallest temperature change upon gaining 200.0 J of heat?

Determine the final temperature of a gold nugget (mass = 376 g) that starts at 398 K and loses 4.85 kJ of heat to a snowbank when it is lost.The specific heat capacity of gold is 0.128 J/g°C.

Use the bond energies provided to estimate ΔH°_rxn for the reaction below. C₂H₄(g) + H₂(g) → C₂H₆(g) ΔH°_rxn = ? Bond Bond Energy (kJ/mol) C-C 347 C-H 414 C=C 611 C≡C 837 H-H 436

Identify what a bomb calorimeter measures.

Use the bond energies provided to estimate ΔH°_rxn for the reaction below. PCl₃(g) + Cl₂(g) → PCl₅(l) ΔH°_rxn = ? Bond Bond Energy (kJ/mol) Cl-Cl 243 P-Cl 331

Identify an element that is NOT in its standard state.

A 6.55 g sample of aniline (C₆H₅NH₂,molar mass = 93.13 g/mol) 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. 4 C₆H₅NH₂(l) + 35 O₂(g) → 24 CO₂(g) + 14 H₂O(g) + 4 NO₂(g) ΔH°_rxn = -1.28 × 10⁴ kJ

According to the following thermochemical equation,what mass of H₂O (in g) must form in order to produce 488 kJ of energy? SiO₂(s) + 4 HF(g) → SiF₄(g) + 2 H₂O(l) ΔH°_rxn = -184 kJ

The temperature rises from 25.00°C to 29.00°C in a bomb calorimeter when 3.50 g of sucrose undergoes combustion in a bomb calorimeter.Calculate ΔE_rxn for the combustion of sucrose in kJ/mol sucrose.The heat capacity of the calorimeter is 4.90 kJ/°C.The molar mass of sugar is 342.3 g/mol.

Two solutions,initially at 24.60°C,are mixed in a coffee cup calorimeter (C_cal = 15.5 J/°C) .When a 100.0 mL volume of 0.100 M AgNO₃ solution is mixed with a 100.0 mL sample of 0.200 M NaCl solution,the temperature in the calorimeter rises to 25.30°C.Determine the DH°_rxn for the reaction as written below.Assume that the density and heat capacity of the solutions is the same as that of water. NaCl(aq) + AgNO₃(aq) → AgCl(s) + NaNO₃(aq) DH°_rxn = ?

How much heat is absorbed when 45.00 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? 5 C(s) + 2 SO₂(g) → CS₂(l) + 4 CO(g) ΔH° = 239.9 kJ

Which of the following processes is exothermic?

Using the following equation for the combustion of octane,calculate the amount of grams of carbon dioxide formed from 100.0 g of octane.The molar mass of octane is 114.33 g/mole.The molar mass of carbon dioxide is 44.0095 g/mole. 2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O ΔH°_rxn = -11018 kJ

Which of the following is NOT a standard state?