The reaction between sodium hydroxide and hydrobromic acid is represented in the equation below:
OH- + H+ -> H2O
A 62.5 mL sample of 1.86 M NaOH at 22.5 deg Celsius was mixed with 62.5 mL sample of 1.86 M of HBr at 22.5 deg Celsius in a coffee cup calorimeter. The temperature increased from 22.5-34.9 degrees. Assume that the volumes are additive, that the specific heat of the solution is the same as that of water, and that the density of the solution is 1.00g/mL
a. Find the amount of heat lost or gained by the calorimeter
b. Find the heat of reaction, when one mole of sodium hydroxide, NaOH, reacts with one mole of hyrdobromic acid in water.
c. Is the reaction endothermic or exothermic?
d. Was energy conserved in the process?
for a) I got 6485.2 joules lost
for b), I don't know how to do this so an explanation would be great:)
for c) I got endothermic
for d) I said that energy was conserved
are my answers correct? im trying to study for a test and I would like to make sure that I am doing this right:)
6485.2 J is right and it is lost BUT by the reaction and not the calorimeter. Since the calorimeter changed T from 22.5 UP TO 34.9 that means the calorimeter gained heat and that means the reaction is exothermic (it released the heat which the calorimeter absorbed).
b. How many mols reacted. That's M x L = 1.86 x 0.0625 = 0.11625
So rxn released 6485.2 J/0.11625 mol = ? J/mol
c. The reaction is exothermic as discussed in part a.
d. d is ok.
Well, let's clown around with your answers and see if they're correct!
a) The amount of heat lost or gained by the calorimeter can be calculated using the formula Q = mcΔT, where Q is the heat, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature. Since the density of the solution is 1.00g/mL, you can assume that the mass is equal to the volume.
So, the mass of the solution is 62.5 mL + 62.5 mL = 125 mL = 125 g. Assuming the specific heat capacity of water is 4.18 J/g°C (like a party in a cup), the change in temperature is 34.9 - 22.5 = 12.4 °C.
Now, plug those values into the formula: Q = (125 g)(4.18 J/g°C)(12.4 °C). Calculate that, and you'll find the answer!
b) Ah, the heat of reaction! This can be calculated by dividing the amount of heat gained or lost (Q) by the number of moles of the limiting reactant (the one you have less of).
First, you need to find the number of moles of the limiting reactant. You can do this using the equation: moles = concentration x volume. Since the concentration of both NaOH and HBr is 1.86 M, and the volume of each is 62.5 mL, you'll find the moles of each reactant.
Since the reaction is 1:1 between NaOH and HBr, the number of moles of the limiting reactant is the same for both. Divide Q by the number of moles of the limiting reactant, and voila!
c) You said the reaction is endothermic, and you're right! The temperature increased, so heat was absorbed from the surroundings. It's like the reaction was chilling on a beach, soaking up some sun.
d) Ah, energy conservation, the golden principle of the universe! Energy can neither be created nor destroyed, it just likes to party and change forms. So yes, energy is conserved in the process.
So, let's summarize our clownish calculations:
a) 6485.2 J of heat lost.
b) Calculate moles of limiting reactant and divide Q by that.
c) Endothermic reaction, like the reaction was a beach bum soaking up heat.
d) Energy conserved, because energy just wants to party and change forms.
Hope that helps! Good luck with your test, and remember, laughter is the best chemistry!
a) To find the amount of heat lost or gained by the calorimeter, you can use the formula:
q = mcΔT
Where,
q = heat (in joules)
m = mass (in grams)
c = specific heat capacity (in J/g°C)
ΔT = change in temperature (in °C)
Since the density of the solution is given as 1.00 g/mL and the volume of the solution is 62.5 mL, the mass of the solution can be calculated as:
mass = volume x density
mass = 62.5 mL x 1.00 g/mL
mass = 62.5 g
Assuming the specific heat capacity of water, c, is 4.18 J/g°C, the ΔT is (34.9 - 22.5) = 12.4 °C.
Therefore, the amount of heat lost or gained by the calorimeter is:
q = (62.5 g) x (4.18 J/g°C) x (12.4 °C)
q = 3232.75 J
So, the amount of heat lost or gained by the calorimeter is 3232.75 joules.
Your answer of 6485.2 joules lost seems incorrect, please review your calculations.
b) To find the heat of reaction, you can use the formula:
heat of reaction = q / moles of limiting reactant
First, determine the moles of the limiting reactant. Since both NaOH and HBr have the same concentration and volume, the number of moles of each is equal to:
moles = concentration x volume
moles of NaOH = (1.86 M) x (0.0625 L)
moles of NaOH = 0.11625 mol
moles of HBr = (1.86 M) x (0.0625 L)
moles of HBr = 0.11625 mol
Since the reaction is a 1:1 ratio, the number of moles of the limiting reactant is 0.11625 mol.
Therefore, the heat of reaction is:
heat of reaction = 3232.75 J / 0.11625 mol
heat of reaction = 27792.47 J/mol
So, the heat of reaction when one mole of NaOH reacts with one mole of HBr in water is 27792.47 joules/mol.
c) Since the temperature increased, the reaction is taking in heat from the surroundings. This indicates that the reaction is endothermic.
Your answer of endothermic is correct.
d) Energy is conserved in the process. This is because energy can neither be created nor destroyed; it can only be transferred or converted from one form to another. In this case, the heat gained by the solution is equal to the heat lost by the calorimeter, thus conserving energy.
Your answer of energy being conserved is correct.
To check your answers, let's go through each question step by step:
a) Finding the amount of heat lost or gained by the calorimeter:
To determine the heat lost or gained by the calorimeter, we can use the formula:
q = m * c * ΔT
where:
q is the heat exchanged
m is the mass of the solution (which we can calculate using the density of the solution)
c is the specific heat of the solution (since it is assumed to be the same as water, which is approximately 4.18 J/g°C)
ΔT is the change in temperature (34.9 - 22.5 = 12.4°C)
Now, let's calculate the mass of the solution:
mass = volume * density
mass = (62.5 mL + 62.5 mL) * 1.00 g/mL
mass = 125 g
q = 125 g * 4.18 J/g°C * 12.4°C
q ≈ 6488.5 J
So, the amount of heat lost or gained by the calorimeter is approximately 6488.5 J.
It seems you made a slight calculation error, as you obtained 6485.2 J, while the correct answer is approximately 6488.5 J.
b) Finding the heat of reaction:
To find the heat of reaction when one mole of NaOH reacts with one mole of HBr, we can use the equation:
q = ΔH * n
where:
q is the heat exchanged (which we calculated in part a)
ΔH is the heat of reaction (what we're trying to find)
n is the number of moles of the limiting reactant (in this case, either NaOH or HBr)
Since the reaction is between NaOH and HBr, they have a 1:1 mole ratio. So, we need to find the number of moles of the limiting reactant. To do this, we can use the formula:
moles = M * volume
where:
M is the molarity (1.86 M)
volume is in liters (convert from mL to L)
For NaOH:
moles_NaOH = 1.86 M * (62.5 mL / 1000 mL/L)
moles_NaOH ≈ 0.116 mol
For HBr:
moles_HBr = 1.86 M * (62.5 mL / 1000 mL/L)
moles_HBr ≈ 0.116 mol
Since they have the same number of moles, either one can be used.
Now, we can calculate the heat of reaction:
6488.5 J = ΔH * 0.116 mol
ΔH ≈ 55988.8 J/mol
Therefore, the heat of reaction when one mole of NaOH reacts with one mole of HBr is approximately 55988.8 J/mol.
c) Determining if the reaction is endothermic or exothermic:
Since the temperature increased during the reaction, it means that heat was absorbed from the surroundings. Therefore, the reaction is endothermic.
Your answer of endothermic is correct.
d) Checking if energy was conserved:
In this case, energy was conserved since no energy was lost to the surroundings. The heat loss by the calorimeter is equal to the heat gained or absorbed by the reaction. Therefore, the total energy in the system remained constant.
Your answer of energy being conserved is correct.
Overall, your answers for parts c and d are correct. However, there was a slight calculation error in part a, where the correct answer is approximately 6488.5 J. The explanation for part b should help you understand the calculation process step by step.