cThe price of gold is $625 per troy ounce at this writing. How much heat (in J) is needed to raise the temperature of $5000.00 worth of gold from 29.5 oC to 70.5 oC?
(1 troy oz = 31.10 g and the specific heat of Au is 25.42 J/(moloC).)
I got 5.125, which isn't right.
Dissolving 7.19 g of CaCl2 in enough water to make 377 mL of solution causes the temperature of the solution to increase by 3.32 oC. Assume the specific heat of the solution and density of the solution are the same as water′s (about 4.18 J/goC and 1.00 g/cm3, respectively) Calculate ΔH per mole of CaCl2 (in kJ) for the reaction under the above conditions.
I got 80.76, which also isn't right.
The thermochemical equation for the burning of ethyl alcohol is
C2H5OH(l) + 3O2(g) --> 2CO2(g) + 3H2O(l) ΔH = -1,367 kJ
What is the enthalpy change (in kJ) for burning 3.20 g of ethyl alcohol?
I got 94.95
A reaction that is used to propel rockets is N2O4(l) + 2N2H4(l) --> 3N2(g) + 4H2O(g). This reaction has the advantage that neither product is toxic, so no dangerous pollution is released. When the reaction consumes 10.0 g of liquid N2O4, it releases 124 kJ of heat. What is the value of ΔH (in kJ per mole N2O4) for the chemical equation as written
1140
Any help is appreciated!
$625/oz x ?oz = $5,000
Solve for ?oz
?oz x 31.1 g/oz = x grams.
q = grams x specific heat Au x (Tfinal-Tinitial)
Make sure mass and specific heat are in the same units.
To solve these problems, we will use the principles of thermodynamics and the formulas for heat and energy calculations. Make sure to double-check your calculations to ensure accuracy.
1. Calculation of heat required to raise the temperature of gold:
To calculate the heat (Q) required to raise the temperature of a substance, we use the formula:
Q = m x c x ΔT
Where:
Q is the heat (in J),
m is the mass of the substance (in g),
c is the specific heat capacity of the substance (in J/(g°C)), and
ΔT is the change in temperature (in °C).
Given:
Price of gold = $625 per troy ounce
1 troy ounce = 31.10 g
Specific heat of Au = 25.42 J/(mol·°C)
Mass of gold = $5000.00 (unknown in g) - We need to calculate this.
First, convert the price of gold to the amount of gold in grams:
31.10 g of gold costs $625.
So, for $5000.00, the mass of gold can be calculated as follows:
Mass of gold = ($5000.00 / $625) x 31.10 g
Next, calculate the heat required:
Q = mass of gold x specific heat of gold x ΔT
ΔT = final temperature - initial temperature
ΔT = 70.5 oC - 29.5 oC
Substitute the known values into the equation and solve for Q.
2. Calculation of ΔH per mole of CaCl2:
To calculate the enthalpy change (ΔH) per mole of a substance using heat calculations, we use the formula:
ΔH = Q / (moles of substance)
Given:
Mass of CaCl2 = 7.19 g
Density of the solution = 1.00 g/cm^3
Volume of the solution = 377 mL = 377 cm^3
Temperature change = 3.32 °C
Specific heat of water = 4.18 J/(g·°C)
First, calculate the moles of CaCl2:
Molar mass of CaCl2 = 40.08 g/mol (40.08 g/mol for Ca + 2 * 35.45 g/mol for Cl)
moles of CaCl2 = mass of CaCl2 / molar mass of CaCl2
Next, calculate the heat using the formula:
Q = mass of solution x specific heat of water x temperature change
The mass of the solution can be calculated as follows:
mass of solution = volume of solution x density of solution
Now substitute the known values into the equation and solve for ΔH.
3. Calculating the enthalpy change for burning 3.20 g of ethyl alcohol:
Given:
Mass of ethyl alcohol = 3.20 g
ΔH = -1,367 kJ (negative sign denotes energy release)
First, calculate the number of moles of ethyl alcohol:
Molar mass of C2H5OH = 2 * 12.01 g/mol + 6 * 1.01 g/mol + 16.00 g/mol = 46.07 g/mol
moles of ethyl alcohol = mass of ethyl alcohol / molar mass of ethyl alcohol
Next, use the ΔH value to calculate the enthalpy change:
ΔH = ΔH per mole x moles of ethyl alcohol
Substitute the known values and solve for ΔH.
4. Calculation of ΔH for the chemical equation of N2O4(l) + 2N2H4(l) --> 3N2(g) + 4H2O(g):
Given:
Mass of N2O4 consumed = 10.0 g
Heat released (Q) = 124 kJ
First, calculate the number of moles of N2O4:
Molar mass of N2O4 = 2 * 14.01 g/mol + 4 * 16.00 g/mol = 92.02 g/mol
moles of N2O4 = mass of N2O4 consumed / molar mass of N2O4
Finally, calculate ΔH:
ΔH = Q / moles of N2O4
Substitute the known values into the equation and solve for ΔH.
Remember to use the correct units and double-check your calculations to ensure accuracy.