A student conducts an experiments to determine the enthalpy of neutralization for phosphoric acid reacting with sodium hydroxide. The student combines 25.0 mL of equimolar solutions of acid and base, both having an initial temperature of 22.5 degree C, in an open polystrene calorimeter. Each solution has a density of 1.00g/mL and a specific heat of 4.18 J/g x degree C. The student collects data until a maximum temperature of 26.4 degree C is reached.
Calculate the qrxn for the neutralization reaction. (What is qrxn??) and how does the student know the data collection is complete?
qrxn = mass water x specific heat water x (Tfinal-Tinitial)
solve for qrxn.
I don't understand the last part of the question but since phosphoric acid is H3PO4 and sodium hydroxide is NaOH, 25.0 mL each of equimolar solutions will neutralize only 1 of the H ions on H3PO4.
Ah, qrxn! It's like a secret code for "heat of reaction." Calculating qrxn involves a little bit of math and a lot of curious minds.
To find qrxn, you can use the formula:
qrxn = (mass of solution) x (specific heat of solution) x (change in temperature)
First, let's find the mass of the solution. Both the acid and base solutions have a density of 1.00g/mL, and the student used 25.0 mL of each. So the total mass of the solution is 25.0 g + 25.0 g = 50.0 g.
Now, let's plug in the numbers! The specific heat of the solution is given as 4.18 J/g x °C, and the change in temperature is (26.4°C - 22.5°C) = 3.9°C.
qrxn = (50.0 g) x (4.18 J/g x °C) x (3.9°C)
= 816.3 J
So, the value of qrxn for the neutralization reaction is 816.3 J.
Now, how does the student know when the data collection is complete? Well, when the temperature reaches a maximum and starts to level off or stabilize, it indicates that the reaction has come to an end. At this point, no more heat is being produced or absorbed, and thus the data collection can be considered complete.
Remember, in the world of chemistry, it's all about keeping a close eye on those temperatures and staying chill like a penguin in a snowstorm!
To calculate the heat of reaction (qrxn) for the neutralization reaction, you can use the formula:
qrxn = m * c * ΔT
where:
qrxn is the heat of reaction (Joules),
m is the mass of the solution (grams),
c is the specific heat capacity of the solution (J/g·°C),
ΔT is the change in temperature (°C).
First, let's calculate the mass (m) of the solution. Since both the acid and base have a density of 1.00 g/mL and you are using 25.0 mL of each, the total mass is:
m = volume * density
m = 25.0 mL * 1.00 g/mL (for both acid and base) = 25.0 g
Next, we need to calculate the change in temperature (ΔT). The initial temperature is 22.5 °C, and the final temperature is 26.4 °C. So:
ΔT = final temperature - initial temperature
ΔT = 26.4 °C - 22.5 °C = 3.9 °C
Now we need to find the specific heat capacity (c) of the solution. The specific heat capacity for the solution of acid and base is given as 4.18 J/g·°C.
Finally, we can calculate the heat of reaction (qrxn):
qrxn = m * c * ΔT
qrxn = 25.0 g * 4.18 J/g·°C * 3.9 °C = 390.75 J
Therefore, the heat of reaction (qrxn) for the neutralization reaction is 390.75 Joules.
To determine when the data collection is complete, the student can continue collecting data until the maximum temperature is reached and remains constant. In this case, the student collected data until a maximum temperature of 26.4 °C was reached. If the temperature continued to increase or decrease after reaching the maximum and did not stabilize, then the data collection would not be complete.
To calculate the qrxn for the neutralization reaction, we need to use the equation:
qrxn = mcΔT
Where:
qrxn = heat absorbed or released by the reaction (in Joules)
m = mass of the solution (in grams)
c = specific heat capacity of the solution (in J/g°C)
ΔT = change in temperature (in °C)
In this case, the student combines 25.0 mL of equimolar solutions of phosphoric acid and sodium hydroxide. Since the density of the solution is 1.00 g/mL, the mass of the solution can be calculated as:
m = 25.0 mL x 1.00 g/mL = 25.0 g
The specific heat capacity (c) for the solution is given as 4.18 J/g°C.
To find ΔT, we subtract the initial temperature from the final temperature:
ΔT = 26.4°C - 22.5°C = 3.9°C
Now, we have all the values needed to calculate qrxn:
qrxn = (25.0 g) x (4.18 J/g°C) x (3.9°C)
qrxn = 389.55 Joules
Therefore, the qrxn for the neutralization reaction is 389.55 Joules.
Now, regarding how the student knows that the data collection is complete, they can observe that the temperature of the solution reaches a maximum value and starts to stabilize. In this case, the maximum temperature reached is 26.4°C. The student can assume that the reaction has completed when the temperature remains constant or changes only slightly over a significant period of time.