Question 1

In the presence of excess oxygen,methane gas burns in a constant pressure system to yield carbon dioxide and water: $\mathrm { CH } _ { 4 }$ (g)+ $2 \mathrm { O } _ { 2 }$ (g)? $\mathrm { CO } _ { 2 }$ (g)+ $2 \mathrm { H } _ { 2 }$ O (l) $\Delta _ { \mathrm { r } }$ H = -890.0 kJ Calculate the value of q (kJ)in this exothermic reaction when 1.90 g of methane is combusted at constant pressure.

Accepted Answer

The molar mass of methane (CH₄) is 16.04 g/mol. For 1.90 g of CH₄, the moles are 1.90 g / 16.04 g/mol = 0.1185 mol. The reaction releases 890.0 kJ per mole of CH₄, so q = 0.1185 mol × (-890.0 kJ/mol) = -105.465 kJ, which rounds to -106 kJ.

Question 2

A 50.0 g sample of liquid water at 25.0 °C is mixed with 19.0 g of water at 87.0 °C.The final temperature of the water is ________°C.

Accepted Answer

The answer of A 50.0 g sample of liquid water...

Question 3

At 1.0133 bar,the heat of sublimation of gallium is 277 kJ $\mathrm { mol } ^ { - 1 }$ and the heat of vaporization is 271 kJ $\mathrm { mol } ^ { - 1 }$ .To the correct number of significant figures,how much heat is required to melt 5.50 mol of gallium at 1.0133 bar?

Accepted Answer

The heat of fusion can be calculated by subtracting the heat of vaporization from the heat of sublimation: 277 kJ/mol - 271 kJ/mol = 6 kJ/mol. For 5.50 mol, the heat required is 5.50 mol * 6 kJ/mol = 33 kJ.

Question 4

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?

Accepted Answer

The heat absorbed (q) is calculated using the formula q = mcΔT, where m is mass, c is specific heat, and ΔT is the change in temperature. Rearranging for ΔT gives ΔT = q / (mc). Substituting the given values: ΔT = 4689 J / (34.2 g * 0.385 J/g°C) = 356°C. Adding the initial temperature (21°C) gives a final temperature of 377°C.

Question 5

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?

Accepted Answer

The answer of The specific heat capacity of methane gas...

Question 6

What is the enthalpy change (in kJ)of a chemical reaction that raises the temperature of 250.0 mL of solution having a density of 1.25 g $\mathrm { mL } ^ { - 1 }$ by 10.2 °C? (The specific heat of the solution is 3.733 J $g ^ { - 1 }$ $\mathrm { K } ^ { - 1 }$ .)

Accepted Answer

The answer of What is the enthalpy change (in kJ)of...

Question 7

Where does the energy absorbed during an endothermic reaction go?

Accepted Answer

The answer of Where does the energy absorbed during an...

Question 8

When 50.0 mL of 0.400 mol L^-1 Ca(NO₃)₂ is added to 50.0 mL of 0.800 mol L^-1 NaF,CaF₂ precipitates,as shown in the net ionic equation below.The initial temperature of both solutions is 24.0 °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 $g ^ { - 1 }$ ${ } ^ { \circ } \mathrm { C } ^ { - 1 }$ ,calculate the final temperature of the solution. Ca²⁺(aq)+ 2F^-(aq)? CaF₂(s) $\Delta _ { \mathrm { r } }$ H = -11.5 kJ

Accepted Answer

First, let's calculate the heat released by the reaction using the given enthalpy change and the moles of limiting reactant (Ca(NO3)2) used:

n(Ca(NO3)2) = 0.0500 L * 0.400 mol/L = 0.0200 mol
ΔH = -11.5 kJ/mol
q = ΔH * n = -11.5 kJ/mol * 0.0200 mol = -0.230 kJ

Since q = m * c * ΔT, we can solve for ΔT:

m = 100.00 g
c = 4.18 J/(g°C)
ΔT = q / (m * c) = -0.230 kJ / (100.00 g * 4.18 J/(g°C)) = -0.0549°C

Finally, we can calculate the final temperature by adding the change in temperature to the initial temperature:

Tf = Ti + ΔT = 24.0°C - 0.0549°C = 23.95°C ≈ 24.55°C (rounded to two decimal places)
Therefore, the answer is B.

Question 9

Sodium metal reacts with water to produce hydrogen gas and sodium hydroxide according to the chemical equation shown below.When 0.015 mol of Na is added to 100.00 g of water,the temperature of the resulting solution rises from 25.00 °C to 31.45 °C.If the specific heat of the solution is 4.18 J $g ^ { - 1 }$ ${ } ^ { \circ } \mathrm { C } ^ { - 1 }$ ,calculate ?H for the reaction,as written. 2Na(s)+ 2H₂O(l)? 2NaOH(aq)+ H₂(g) $\Delta _ { \mathrm { r } }$ H= ?

Accepted Answer

The answer of Sodium metal reacts with water to produce...

Question 10

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

Accepted Answer

First, we need to find the amount of moles of C(s) used in the reaction. 
Molar mass of C(s) = 12.01 g/mol 
n(C) = 50.00 g/12.01 g/mol = 4.165 mol

According to the balanced chemical equation, the reaction produces 239.9 kJ of heat per 5 moles of C(s) reacted. 
So, for 4.165 mol of C(s) reacted, the heat absorbed can be calculated as: 
Heat absorbed = (4.165 mol / 5 mol) x 239.9 kJ 
Heat absorbed = 199.7 kJ/mol

Therefore, the answer is A) 199.7 kJ/mol.

Question 11

When 1.50 mol of CH₄(g)reacts with excess Cl₂(g)at constant pressure according to the chemical equation shown below,1062 kJ of heat are released.Calculate the value of ?H for this reaction,as written. 2CH₄(g)+ 3Cl₂(g)? 2CHCl₃(l)+ 3H₂(g) $\Delta _ { \mathrm { r } }$ H° = ?

Accepted Answer

The reaction releases 1062 kJ of heat for 1.50 mol of CH4. Since the balanced equation involves 2 mol of CH4, the enthalpy change for the reaction as written is (1062 kJ / 1.50 mol) * 2 mol = -1416 kJ, which is closest to -1420 kJ/mol.

Question 12

At constant pressure,the combustion of 20.0 g of C₂H₆(g)releases 1036 kJ of heat.What is ?H for the reaction given below? 2C₂H₆(g)+ 7O₂(g)? 4CO₂(g)+ 6H₂O(l)

Accepted Answer

The answer of At constant pressure,the combustion of 20.0 g...

Question 13

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?

Accepted Answer

The molar mass of hydrogen peroxide (H2O2) is 34.01 g/mol. For 4.00 g, the moles are 4.00 g / 34.01 g/mol = 0.1176 mol. The reaction releases -196 kJ for 2 moles, so for 0.1176 mol, q = -196 kJ * (0.1176 mol / 2 mol) = -11.5 kJ.

Question 14

8.000 moles of H₂(g)reacts with 4.000 mol of O₂(g)to form 8.000 mol of H₂O(l)at 25 °C and a constant pressure of 1.0133 bar.If 546.4 kJ of heat are released during this reaction,and PΔV is equal to -29.60 kJ,then

Accepted Answer

The correct answer is based on the understanding that ΔH (enthalpy change) and ΔU (internal energy change) are related by the equation ΔH = ΔU + PΔV. Given that 546.4 kJ of heat are released, ΔH° = -546.4 kJ (since release of heat is exothermic and thus negative). With PΔV = -29.60 kJ, to find ΔU, we rearrange the equation to ΔU = ΔH - PΔV = -546.4 kJ - (-29.60 kJ) = -516.8 kJ.

Question 15

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) $\Delta _ { \mathrm { r } } H$ = ?

Accepted Answer

The heat absorbed by the solution can be calculated using q = mcΔT, where m is the mass of the solution (102.50 g), c is the specific heat (4.18 J/g°C), and ΔT is the temperature change (18.32°C). This gives q = 102.50 g * 4.18 J/g°C * 18.32°C = 7850.67 J or 7.85 kJ. Since the reaction releases heat, ΔH is negative. The moles of Ba is 2.50 g / 137.33 g/mol = 0.0182 mol. ΔH per mole is -7.85 kJ / 0.0182 mol = -431 kJ/mol.

Question 16

Describe the energy changes that occur when a book is held 1 m off the floor and then dropped.

Accepted Answer

The answer of Describe the energy changes that occur when...

Question 17

How much heat is absorbed/released when 40.00 g of NH₃(g)reacts in the presence of excess $\mathrm { O } _ { 2 }$ (g)to produce NO(g)and H₂O(l)according to the following chemical equation? 4NH₃(g)+ 5O₂(g)? 4NO(g)+ 6H₂O(l) $\Delta _ { \mathrm { r } }$ H° = 1168 kJ

Accepted Answer

The given chemical equation shows that the reaction of 4 moles of NH₃(g) with 5 moles of O2(g) releases 1168 kJ of heat. To calculate the heat released for the given amount (40.00 g) of NH₃(g), we need to first calculate the number of moles of NH₃(g) using its molar mass: Molar mass of NH₃(g) = 14.007 + 1.008 + 32.06 = 47.07 g/mol Number of moles of NH₃(g) = 40.00 g / 47.07 g/mol = 0.8495 mol From the balanced chemical equation, we see that 4 moles of NH₃(g) release 1168 kJ of heat. So, for 0.8495 mol of NH₃(g), the heat released can be calculated as: Heat released = (1168 kJ / 4 mol) x 0.8495 mol = 311.13 kJ However, the question is asking for the heat absorbed/released, which means we need to look at the sign of the given enthalpy change. The enthalpy change ($\Delta _ { \mathrm { r } }$ H°) is positive, which means heat is absorbed during the reaction. Therefore, the correct answer is A) 685.8 kJ of heat are absorbed.

Question 18

Define chemical energy.

Accepted Answer

The answer of Define chemical energy....

Question 19

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

Accepted Answer

The first law of thermodynamics states that ΔU = q + w, where ΔU is the change in internal energy, q is the heat added to the system, and w is the work done by the system. Here, ΔU = 145 kJ + (-35 kJ) = 110 kJ. For a process at constant pressure, the enthalpy change ΔH is equal to the heat added to the system, so ΔH = 145 kJ.

Question 20

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 $\mathrm { mol } ^ { - 1 }$ .

Accepted Answer

The heat absorbed by the calorimeter is calculated using q = C × ΔT, where C is the heat capacity and ΔT is the temperature change. The heat of reaction is then calculated per mole of Ti, considering the molar mass of Ti and the heat absorbed.

Quiz 6: Thermochemistry

A 50.0 g sample of liquid water at 25.0 °C is mixed with 19.0 g of water at 87.0 °C.The final temperature of the water is ________°C.

At 1.0133 bar,the heat of sublimation of gallium is 277 kJ $\mathrm { mol } ^ { - 1 }$ and the heat of vaporization is 271 kJ $\mathrm { mol } ^ { - 1 }$ .To the correct number of significant figures,how much heat is required to melt 5.50 mol of gallium at 1.0133 bar?

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?

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?

What is the enthalpy change (in kJ) of a chemical reaction that raises the temperature of 250.0 mL of solution having a density of 1.25 g $\mathrm { mL } ^ { - 1 }$ by 10.2 °C? (The specific heat of the solution is 3.733 J $g ^ { - 1 }$ $\mathrm { K } ^ { - 1 }$ .)

Where does the energy absorbed during an endothermic reaction go?

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

When 1.50 mol of CH₄(g) reacts with excess Cl₂(g) at constant pressure according to the chemical equation shown below,1062 kJ of heat are released.Calculate the value of ?H for this reaction,as written. 2CH₄(g) + 3Cl₂(g) ? 2CHCl₃(l) + 3H₂(g) $\Delta _ { \mathrm { r } }$ H° = ?

At constant pressure,the combustion of 20.0 g of C₂H₆(g) releases 1036 kJ of heat.What is ?H for the reaction given below? 2C₂H₆(g) + 7O₂(g) ? 4CO₂(g) + 6H₂O(l)

8.000 moles of H₂(g) reacts with 4.000 mol of O₂(g) to form 8.000 mol of H₂O(l) at 25 °C and a constant pressure of 1.0133 bar.If 546.4 kJ of heat are released during this reaction,and PΔV is equal to -29.60 kJ,then

Describe the energy changes that occur when a book is held 1 m off the floor and then dropped.

How much heat is absorbed/released when 40.00 g of NH₃(g) reacts in the presence of excess $\mathrm { O } _ { 2 }$ (g) to produce NO(g) and H₂O(l) according to the following chemical equation? 4NH₃(g) + 5O₂(g) ? 4NO(g) + 6H₂O(l) $\Delta _ { \mathrm { r } }$ H° = 1168 kJ

Define chemical energy.

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

Quiz 6: Thermochemistry

A 50.0 g sample of liquid water at 25.0 °C is mixed with 19.0 g of water at 87.0 °C.The final temperature of the water is ________°C.

At 1.0133 bar,the heat of sublimation of gallium is 277 kJ mol−1\mathrm { mol } ^ { - 1 }mol−1 and the heat of vaporization is 271 kJ mol−1\mathrm { mol } ^ { - 1 }mol−1 .To the correct number of significant figures,how much heat is required to melt 5.50 mol of gallium at 1.0133 bar?

The specific heat of copper is 0.385 J g−1g ^ { - 1 }g−1 K−1\mathrm { K } ^ { - 1 }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?

The specific heat capacity of methane gas is 2.20 J g−1g ^ { - 1 }g−1 K−1\mathrm { K } ^ { - 1 }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?

What is the enthalpy change (in kJ) of a chemical reaction that raises the temperature of 250.0 mL of solution having a density of 1.25 g mL−1\mathrm { mL } ^ { - 1 }mL−1 by 10.2 °C? (The specific heat of the solution is 3.733 J g−1g ^ { - 1 }g−1 K−1\mathrm { K } ^ { - 1 }K−1 .)

Where does the energy absorbed during an endothermic reaction go?

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) Δr\Delta _ { \mathrm { r } }Δr​ H° = 239.9 kJ

When 1.50 mol of CH4(g) reacts with excess Cl2(g) at constant pressure according to the chemical equation shown below,1062 kJ of heat are released.Calculate the value of ?H for this reaction,as written. 2CH4(g) + 3Cl2(g) ? 2CHCl3(l) + 3H2(g) Δr\Delta _ { \mathrm { r } }Δr​ H° = ?

At constant pressure,the combustion of 20.0 g of C2H6(g) releases 1036 kJ of heat.What is ?H for the reaction given below? 2C2H6(g) + 7O2(g) ? 4CO2(g) + 6H2O(l)

8.000 moles of H2(g) reacts with 4.000 mol of O2(g) to form 8.000 mol of H2O(l) at 25 °C and a constant pressure of 1.0133 bar.If 546.4 kJ of heat are released during this reaction,and PΔV is equal to -29.60 kJ,then

Describe the energy changes that occur when a book is held 1 m off the floor and then dropped.

How much heat is absorbed/released when 40.00 g of NH3(g) reacts in the presence of excess O2\mathrm { O } _ { 2 }O2​ (g) to produce NO(g) and H2O(l) according to the following chemical equation? 4NH3(g) + 5O2(g) ? 4NO(g) + 6H2O(l) Δr\Delta _ { \mathrm { r } }Δr​ H° = 1168 kJ

Define chemical energy.

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

At 1.0133 bar,the heat of sublimation of gallium is 277 kJ $\mathrm { mol } ^ { - 1 }$ and the heat of vaporization is 271 kJ $\mathrm { mol } ^ { - 1 }$ .To the correct number of significant figures,how much heat is required to melt 5.50 mol of gallium at 1.0133 bar?

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?

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?

What is the enthalpy change (in kJ) of a chemical reaction that raises the temperature of 250.0 mL of solution having a density of 1.25 g $\mathrm { mL } ^ { - 1 }$ by 10.2 °C? (The specific heat of the solution is 3.733 J $g ^ { - 1 }$ $\mathrm { K } ^ { - 1 }$ .)

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

When 1.50 mol of CH₄(g) reacts with excess Cl₂(g) at constant pressure according to the chemical equation shown below,1062 kJ of heat are released.Calculate the value of ?H for this reaction,as written. 2CH₄(g) + 3Cl₂(g) ? 2CHCl₃(l) + 3H₂(g) $\Delta _ { \mathrm { r } }$ H° = ?

At constant pressure,the combustion of 20.0 g of C₂H₆(g) releases 1036 kJ of heat.What is ?H for the reaction given below? 2C₂H₆(g) + 7O₂(g) ? 4CO₂(g) + 6H₂O(l)

8.000 moles of H₂(g) reacts with 4.000 mol of O₂(g) to form 8.000 mol of H₂O(l) at 25 °C and a constant pressure of 1.0133 bar.If 546.4 kJ of heat are released during this reaction,and PΔV is equal to -29.60 kJ,then

How much heat is absorbed/released when 40.00 g of NH₃(g) reacts in the presence of excess $\mathrm { O } _ { 2 }$ (g) to produce NO(g) and H₂O(l) according to the following chemical equation? 4NH₃(g) + 5O₂(g) ? 4NO(g) + 6H₂O(l) $\Delta _ { \mathrm { r } }$ H° = 1168 kJ