At 298K and 1 bar pressure, the density of water is 0.9970g/cm3, and Cp,m = 75.3 J/K

In summary, at a temperature of 298K and 1 bar pressure, the density of water is 0.9970g/cm3 and the coefficient of thermal expansion is 2.07*10^-4 K^-1. Using the equations dV=V(initial)ßdT and dH = qp = u + w = u + PV, the values of w, q, dH, and dU can be calculated for a 250 g sample of water whose temperature is increased by 38.0K. The final values should be w=-0.197J, q=39700J, dH=39700J, and dU=39700J. The problem can be solved by using the
  • #1
thechamp
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Homework Statement



At 298K and 1 bar pressure, the density of water is 0.9970g/cm3, and Cp,m = 75.3 J/K moL. The change in volume with temperature is given by dV=V(initial)ßdT where ß, the coefficient of thermal expansion is 2.07*10^-4 K^-1 . If the temperature of 250 g of water is increased by 38.0K, calculate w,q,dH,dU



Homework Equations



dV=V(initial)ßdT
dH = qp (heat at constant P) = u + w = u + PV
dU= q + w

The Attempt at a Solution


The answer should be w=-0.197J, q=39700J, dH=39700J, dU= 39700J but I have no idea how to solve this problem. I don't even know where to start...I am completely lost. Please help
 
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  • #2
The unit conversions are a little annoying, but the problem is straightforward for the most part. Use the standard Chem 101 formula for heat ##q=mc\Delta T##
Calculate the change in volume and use that to find the expansion work ##P\Delta V## (make sure to get the sign right!). Then you can use these quantities to get ##\Delta U## and ##\Delta H##.
 

1. What is the significance of the values given for water density and specific heat at 298K and 1 bar pressure?

The values provided for water density and specific heat at 298K and 1 bar pressure are important because they represent the properties of water under standard conditions, which are commonly used as reference points in scientific experiments and calculations.

2. How was the value of 0.9970g/cm3 determined for the density of water at 298K and 1 bar pressure?

The value of 0.9970g/cm3 for water density at 298K and 1 bar pressure was determined through experimental measurements and calculations, using methods such as Archimedes' principle and the ideal gas law.

3. What does the value of Cp,m = 75.3 J/K represent for water at 298K and 1 bar pressure?

The value of Cp,m = 75.3 J/K represents the molar specific heat capacity of water at 298K and 1 bar pressure, which is the amount of energy required to raise the temperature of one mole of water by 1 Kelvin under these conditions. It is a measure of the intrinsic ability of water to store heat energy.

4. How does the density of water at 298K and 1 bar pressure compare to other temperatures and pressures?

The density of water at 298K and 1 bar pressure is considered the standard value, and it varies with changes in temperature and pressure. Generally, water becomes less dense as it increases in temperature and more dense as pressure increases.

5. What are the practical applications of knowing the density and specific heat of water at 298K and 1 bar pressure?

The knowledge of water's density and specific heat at 298K and 1 bar pressure has numerous practical applications, including in industries such as food and beverage, chemical processing, and power generation. It is also important in understanding the behavior of water in natural systems and in the design of experiments and equipment in many scientific fields.

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