First Law of Thermodynamics

A steam turbine uses some form of energy to evaporate water, heat the vapour and move a cylinder. We can think of this a constant pressure process, where $H_2O(l) → H_2O(g)$.

Complete the following sentences about this process by choosing one description per line. Enter the answers separated by a comma in the box below.

This process is exothermic / endothermic.

A system composed of 4.50 L of N2 in a cylinder expands against an external pressure of 300 kPa until its volume is 6.30 L.

A 10.0 g piece of Mg(s) is deposited in a container with a vast excess of HCl(aq). A reaction takes place forming hydrogen gas and Magnesium Chloride.

a) Write a balanced chemical reaction for the transformation

b) Calculate the work done by the system as a consequence of the reaction, if Pex = 1.1 atm and T = 298.15 K. You may assume ideal behaviour.

A fuel compound was burned in oxygen in a bomb calorimeter with a combined heat capacity of 56.5 k] / K (Bomb assembly and water). The temperature of the surrounding water bath increased from 23.5 to 34.6 °C as a result. Calculate $\Delta E_{sys}$for this process? Consider any change in pressure due to gaseous products to be negligible.

2.3 moles of an ideal gas initially at -12oC and 16 atm underwent a complete expansion against a constant external pressure of 1atm and did 1.1kJ of work. Calculate Δ𝑈, Δ𝐻, 𝑎𝑛𝑑 𝑞 for this process.

Which of these reactions involve pressure-volume work being done on the system?

The enthalpy of combustion for ethanol (C2H5OH) is -1370.7 kJ/mol. Calculate q, w and ΔU when 45.0g of ethanol are burned at 1atm and 298K.

Answers need to be in scientific notation, with proper significant figures. Give all values in kJ.

1.8 moles of an ideal gas initially at -5 oC and 1.7 atm underwent a complete expansion against a constant external pressure of 1atm and did 1.1kJ of work. Calculate ∆𝑈, ∆𝐻, 𝑎𝑛𝑑 𝑞 for this process.

Step 1: Extract all relevant information from the problem

Step 2: We have three of four variables for the initial state so we solve for the fourth (R=0.08206Latm/Kmol)

16 grams of dry ice (CO2(s)) was placed in a piston with an initial volume of 4L and allowed to sublimate and warm to room temperature. The system then underwent a reversible isothermal expansion to a final pressure of 1.0 atm. Calculate ΔU, q and w for this process. You can assume that CO2(g) behaves as an ideal gas.

R=0.08206Latm/Kmol

R=8.314J/Kmol

Four moles of an ideal gas originally at 323 oC and 7.3 atm underwent a complete expansion against a constant external pressure of 1 atm and did 8kJ of work. Calculate q, ΔE, ΔH.

Solve for the missing initial variable (Vi):

hint: rearrange PV=nRT to do this!

4 moles of neon was confined to a 8L flask initially at room temperature underwent an isothermal expansion into a vacuum at 348K. Calculate ∆𝑈, ∆𝐻, 𝑎𝑛𝑑 𝑞 for this process.

Isothermal Expansion of an ideal gas:

Free Expansion into a vacuum:

The enthalpy of combustion for ethanol (C2H5OH) is -1370.7 kJ/mol. Calculate q, w, ΔH and ΔU when 45g of ethanol are burned at 1atm and 298K.

Consider the following balanced chemical equation for the combustion of propane, C3H8:

$C_3H_8 (g) + 5 O_2 (g) → 4 H_2O (ℓ) + 3 CO_2 (g) \qquad q < 0$

Use this information to answer the next two questions. Choose one if the options inside the brackets

Which of the following processes always results in a positive change in internal energy of a system?

A freshly baked pie is placed near an open window to cool. Which of the following statements best describes this situation?

From the following reaction:

$2C_6H_{12}O_6(s)+2O_2(g)→12CO_2(g)+4H_2O(l)\qquad \qquad ΔH_{rxn}=-1680kJ/mol\cdot rxn$

When an unknown quantity of sugar (C6H12O6) is burned, it was determined that the internal energy of the system decreased by 960 kJ and that 15.7 kJ of work was done on the system. How many grams of sugar were present at the beginning of this specific reaction?

0.08 mole of nitrogen undergoes the following process. What is the work done on the gas?

A Piston containing an 1.3 moles of an Ideal Gas undergoes a compression from 32 L to 27 L against a constant external pressure of 178 kPa. During this transformation the temperature does not change. Calculate the heat flow, q, for this transformation.

How much heat is required to convert a 15.5 g ice cube at -5.00oC to liquid water at 0oC? (The specific heat of ice is 2.09 J/g K, the specific heat of water is 4.18 J/g K, and the ΔHfus for water=334 J/g).

The combustion of 1.00 mol of glucose (C6H12O6) gives off 2.82x103 kJ of heat (i.e. ΔHcomb = 2.82x103 kJ mol-1). If 1.80 g glucose (molar mass is 180) is burned in a bomb calorimeter and the temperature of the calorimeter increases from 19.00oC to 23.50oC, what is the heat capacity of the calorimeter (kJ/oC)?

A chemical compound has a molecular weight of 89.05 g/mol. 1.400 grams of this compound underwent complete combustion under constant pressure conditions in a calorimeter with a heat capacity of 2.980 × 103 J/ °C. The temperature went up by 11.95 °C. Calculate the standard heat of combustion of the compound.

How much work is performed in Joules when 3.00 mols of N2(g) expands against 1 atm of external pressure via heating from 298 K to 498 K at constant pressure of 1 atm?

From the following reaction:

$2C_6H_{12} O_{6(s)}+2O_{2(g)} \to 12CO_{2(g)}+4H_2O_{(l)} \hspace{20pt} \Delta H_{rxn}=-1680 kJ$

When an unknown quantity of sugar (C6H12O6) is burned, it was determined that the internal energy of the system decreased by 960 kJ and that 15.7 kJ of work was done on the system. How many grams of sugar were present at the beginning of this specific reaction?

How much energy is required to bring 1.00 g of liquid water from 35 °C to 165 °C water vapour? The enthalpy of vaporization of water is +40.7 kJ/mol, the specific heat capacity of liquid water is 4.18 J / g °C, and the specific heat capacity of water vapour is 1.87 J/g °C.

A 10.0 g piece of Mg(s) is deposited in a container with a vast excess of HCl(aq). A reaction takes place forming hydrogen gas and Magnesium Chloride. Write a balanced chemical reaction for the transformation and calculate the work done by the system as a consequence of the reaction, if Pex = 1.1 atm and T = 298.15 K. You may assume ideal behaviour.

A fuel compound was burned in oxygen in a bomb calorimeter with a combined heat capacity of 56.5 kJ / K (Bomb assembly and water). The temperature of the surrounding water bath increased from 23.5 to 34.6 °C as a result. Calculate $\Delta E_{sys}$for this process? Consider any change in pressure due to gaseous products to be negligible.

In an auto shop, a hydraulic piston expands to lift a car into the air so the mechanic can access the oil pan under the car. When the piston expands, which of the following is true? You may consider the piston the system.

An alkane’s vapour pressure at 25.00 °C is 6.00 kPa. What is its vapour pressure at 80.00 °C if the enthalpy of vaporization is 43.0 kJ/mol? (Give your answer in kPa)

Which statement below is INCORRECT?

Which statement below is INCORRECT?

A 2.00 mole sample of a monoatomic ideal gas is initially at 1.00 L and 1.00 atm. Calculate the total q, w, ${\small \Delta\text{E}}$and ${\small \Delta \text{H}}$when the final conditions are 0.500 L and 5.00 atm along the pathway where the volume is compressed first.

[Do NOT include units in your answers]

The enthalpy of combustion for ethanol (C2H5OH) is -1370.7 kJ/mol. Calculate q, w, ΔH and ΔU when 45g of ethanol are burned at 1atm and 298K.

2. If an exothermic process releases 555 J of heat to the surroundings when the volume of the system is kept constant, how would the amount of heat released change if the system were allowed to expand instead?

If an exothermic process releases 555 J of heat to the surroundings when the volume of the system is kept constant, how would the amount of heat released change if the system were allowed to expand instead?

Determine the work done when a gas is allowed to expand from 25.0 L to 50.0 L against a constant pressure of 13.6 atm.

Work equation:

∆V=Vf=Vi

In the following reaction, assuming that the gases behave ideally, calculate the work at 25C and 101.3kPa

Practice: Isothermal Expansion

4 moles of neon was confined to a 8L flask initially at room temperature underwent an isothermal expansion into a vacuum at 348K. Calculate ∆𝑈, ∆𝐻, 𝑎𝑛𝑑 𝑞 for this process.

You have a family of four living in a home. The home has a one large

window with $k=1.05\ \left[\frac{W}{mK}\right],\ A=1.2\ \left[m^2\right]$. The house is

made of wood $k=0.2\left[\frac{W}{mK}\right]$and an exposed area of $A=15\ \left[m^2\right]$.Given an outside temperature of $5\ \degree C$ and an inside temperature of $24\ \degree C$, find the smallest heater than can maintain the internal temperature.

Practice: Work

0.08 mole of nitrogen undergoes the following process. What is the work done on the gas?

Which of the following processes always results in a positive change in internal energy of a system?

Practice: Work Calculation

0.08 mole of nitrogen undergoes the following process. What is the work done on the gas?