Constant pressure Definition and 83 Threads

Homework Statement If 650 J of heat are added to 21 moles of a monatomic gas at constant pressure, how much does the temperature of the gas increase? (in Kelvins) Homework Equations U = nRT Q=(5/2)nR(T2-T1) The Attempt at a Solution well how do you even know how much the...

Why Do I Use U For Constant Volume and H For Constant Pressure? Also, which can be calculated H, Q, U, W?

Homework Statement A sample of 4.00mol of oxygen is originally confined in a 20L vessel at 270K and then undergoes adiabatic expansion against a constant pressure of 600torr until the volume has tripled. Find q, W, dT, dU, dH. Homework Equations U=q+w H=U+PV The Attempt at a Solution q=0...

For a process at constant pressure, ΔH=q. My textbook clearly says that the only way that enthalpy can change is with a change in temperature. So ΔH=0. But q≠0 for an isothermal process. I know that ΔU=0 for an isothermal process. So ΔH=0+Δ(PV)=Δ(nRT)=0 It really seems like ΔH should...

The conversion of propene (C3H6) to dichloromethane (CH2Cl2) takes place according to the reaction C3H6(g) + 3Cl2(g) 6 3CH2Cl2(g). At 298.15 K, the standard enthalpy change of this reaction is -306.98 kJ mol-1 and the standard enthalpy of formation of CH2Cl2(g) is -95.52 kJ mol-1...

Homework Statement I am given the amount of moles of gas, how many joules of heat I put into the system, and a positive change in temperature. Then it says "calculate the molar heat capacities at constant volume and constant pressure of the gas." Homework Equations q=CT, C(constant...

Hello My story Till today, I had never imagined that the High Heat Value (HHV) of fuels or their Lower Heat Value (LVH) have themselves (at least) two variants: - the constant volume heat value - the constant pressure heat value These quantities can be most directly measured in...

i have a rather silly question involving PV = nRT and Charles's Law. Charles's Law states that the volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature of the gas. I'm wondering about how do you maintain a constant pressure of...

Can a thermodynamic system simultaneously exist under both constant volume and constant pressure at a particular instant. I mean , when the system is under constant pressure condition, can we impose constant volume on the system. Please clear my doubt. I don't know if it's a silly question, but...

Homework Statement A vertical cylinder with a heavy piston contains air at 315 K. The initial pressure is 2.85 105 Pa, and the initial volume is 0.250 m3. Take the molar mass of air as 28.9 g/mol and assume CV = 5/2R. (d) Assume again the conditions of the initial state and assume the...

Homework Statement Suppose 15.2 g of oxygen (O2) is heated at constant atmospheric pressure from 13.3°C to 148°C. (a) How many moles of oxygen are present? (Take the molar mass of oxygen to be 32.0 g/mol) (b) How much energy is transferred to the oxygen as heat? (The molecules rotate but do...

Dear Forum members, I have a bit confusion about the "Specific Heat at constant pressure". Normally it only varies with the temperature (As given by many book at their Appendixs). But these values are only given at 1 atm pressure and with a wide range of temperature. Most of the books...

Homework Statement A 30.0mL sample of 0.937M A is mixed with 16.7mL of 0.904M B in a constant pressure calorimeter. The thermochemical equation for this reaction is: A(aq) + B(aq) --> C(aq) + D(aq); ΔH = 41.2kJ Both solutions are at 24.9 degrees Celsius prior to mixing and reacting. What...

Homework Statement 2 moles of gas at 300 K at 0.02 m3 is expanded to twice the original volume at constant pressure, and then adiabatically until T = 300 K again. assume monatomic gas. assume ideal. determine the final volume determine the heat supplied to the overall process determine...

Constant volume or constant pressure?? In a question I tried to solved: "A house has well-insulated walls. It contains a volume of 100 m3 of air at 300 K. Calculate the energy required to increase the temperature of this diatomic ideal gas by 1.00°C." The solution start with the assumption by...

Homework Statement 1m^3 of air is heated reversibly at constant pressure from 288K to 573K. Then it is cooled reversibly at constant volume back to the initial T. Initial P is 103kPa Calculate overall change in entropy. Cp=1.02 Cv=0.702 Homework Equations dS=Cp x ln(T2/T1)-R x...

This is a conceptual question...hope you guys can explain the answers that the book gives! Its frustrating me to no end. This is actually a problem in the Enthalpy chapter, calorimetry section of section exercises of the Olmsted and Williams chemistry textbook, 3rd ed. Any help would be...

I've read that: specific heat capacity at constant pressure = dU-W / m. dT dU = change in internal energy W = work done m = mass of gas dT = change in temperature ----------------------------------- However, shouldn't the right hand side equate to specific heat capacity at...

Homework Statement For temperatures T >> T_C (critical temperature) derive the heat capacity at constant pressure C_P from van der Waals equation. Homework Equations Critical temperature: T_C = \frac{2N(V - Nb)^2}{kV^2} T_C is derived from the fact that it exist at the point in which...

PRoblem statement- The specific heat of silver is 0.235J/gC and the specific heat of water is 4.184J/gC. A piece of silver at 94.31C was dropped into a constant pressure calorimeter containing 148g of water at 24.08C. The final temperature of the water and silver was 25.39C. Assuming that the...

Homework Statement what mass of water could be warmed from 23.8 C to 46.3 C by a 100 g metal pellet at 116 C Homework Equations The Attempt at a Solution well i know the formula qsurr=ms\DeltaT so qwater=ms\DeltaT but then how do i work my way around when the heat capacity isn't also given...

Homework Statement Consider the following two well-mixed, isothermal batch reactors for the elementary and irreversible decomposition of A to B, A\stackrel{k}{\rightarrow}2B reactor1: The reactor volume is constant (Pressure is variable) reactor2: The reactor pressure is constant (Volume is...

A substance is contained within a simple piston-cylinder arrangement, perfectly insulated from the external environment, at a pressure,temperature,volume combination where it exists as a saturated liquid-vapour. If I now expand the volume using the piston, more of the liquid phase should boil...

if i was to heat a gas [any gas] by 10 degrees celcius, using the smallest amount of heat energy, would i be better off heating the gas at constant pressure or constant volume. i think constant pressure, however i don't know how to justify my answer...:confused: cheers

If I apply 200 J of energy as heat to 4 moles of an ideal gas at constant pressure and the temperature rises by 4 K, then the molar heat capacity at constant pressure will be Cp = Q / (n * deltaT) = 200 / (4 x 4) = 12.5 J K mol Am I on the right lines here?

Can someone confirm if my understanding of heat capacity is correct - particulary at constant volume and pressure? My understanding is that for a system to experience a rise in temperature either its pressure or its volume must remain constant. If either of these is allowed to expand...

Homework Statement For a gas of molar mass M, Cp/Cv=y. Find specific heat at constant pressure. The Attempt at a Solution C_p=\frac{Pdv}{ndt}+C_v PV=nRT, P=constant \frac{P}{n} \frac{dv}{dt}=R Substituting in the above equation: C_p(\frac{y-1}{y})=R C_p=\frac{Ry}{y-1}...

Homework Statement 1) How much heat energy must be added to the gaseous mixture consisting of 1 gm of Hydrogen and 1 gm of Helium to raise its temperature from 0 degree C to 100 degree C at constant pressure? Given that g1=1.41, g2=1.67 Homework Equations Heat required = nC(p)dT...

Find the work done by a gas when it is expanded from a volume of 1.0 L to 3.3 L at a constant pressure of 2.8 atm. I converted the atm to Pascals by multiplying 2.8 x 101325 to get 283710. Then I used the formula W=p(deltaV) so 283710 x (3.3-1.0) = 652533 I don't understand why this...

My textbook derived the equation ΔH = ΔE + ΔnRT (H is enthalpy, E is internal energy (heat exchanged + work )) from the fact that ΔH = ΔE + PΔV at constant pressure. This derivation, however, requires that temperature be constant; otherwise, the resulting equation would be ΔH = ΔE + ΔnRΔT (ΔT...

Why is enthalpy so commonly described only in constant pressure situations? It applies to change in pressure environments as well.

Sir, Please help me with this problem. A Volume – Temperature diagram was obtained when a gas was heated at a constant pressure. During the heating process from state 1 to state 2 how does its mass vary? Sometimes the diagram may not clear, so I will try to describe how it looks like. It...

Aren't we doing some work to prevent the gas from expanding if we maintain the constant volume. So shouldn't molar specific heat at constant pressure be equal to constant volume?