Chemistry: Finding a temperature change using a temperature/gram ratio

In summary: First of all, you need to calculate the heat released by the reaction using the formula Q=cm(t2-t1). Then, use the equation q=mC(t2-t1) to find the heat of formation of MgCl2. Finally, divide the heat of formation by the number of moles of MgCl2 to find the temperature change for 1 mol of MgCl2. In summary, the question is asking for the temperature change for 1 mol of MgCl2, using the heat of formation and specific heat of water.
  • #1
Aiko
8
0

Homework Statement


In this investigation, you mix .5g of Mg(s) with 115mL HCl. You measure the temperature change which turns out to be 25.5 degrees C. The equation is as follows:

Mg + 2HCL --> MgCl2 + H2

Use the specific heat of water (c=4.184) to find the heat of formation.

What is the temperature change of 1mol of MgCl2?

Homework Equations


Q=cm(t2-t1)
Kind of basic algebra that I think I'm getting wrong. Or maybe I'm using the wrong variables.

The Attempt at a Solution


This problem uses the specific heat of water. This means that we must use the mass of water as well (1mol = 18g).
Q=4.184(18g)(t2-t1)

I am having trouble with the temperature change. Mg is the limiting reactant. Therefore:

.5g Mg (mol/24.31g) = .021mol Mg (mol MgCl2/mol Mg) = .021mol MgCl2

.021mol MgCl2 (95.21g MgCl2/mol MgCl2) = 1.99941 ~2.00g MgCl2

Therefore:

(25.5C/2.00g MgCl2) * 95.21g MgCl2 = 1214C

This answer however, isn't correct. Am I supposed to use the masses of water instead?
 
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  • #2
Temperature of _what_ has changed?
 
  • #3
Aiko said:

Homework Statement


In this investigation, you mix .5g of Mg(s) with 115mL HCl. You measure the temperature change which turns out to be 25.5 degrees C. The equation is as follows:

Mg + 2HCL --> MgCl2 + H2

Use the specific heat of water (c=4.184) to find the heat of formation.

What is the temperature change of 1mol of MgCl2?

Can anyone help?
 
  • #4
Can you answer the question asked in my previous post?

You are not asked about temperature change of 1 mol of MgCl2, you must have misread the question. This is a classic experiment for determination of molar enthalpy of the reaction.
 

1. What is the purpose of finding a temperature change using a temperature/gram ratio in chemistry?

The purpose of finding a temperature change using a temperature/gram ratio in chemistry is to determine the specific heat capacity of a substance. This is a measure of how much heat energy is required to raise the temperature of a substance by a certain amount.

2. How is the temperature/gram ratio calculated?

The temperature/gram ratio is calculated by dividing the change in temperature (in degrees Celsius or Kelvin) by the mass of the substance (in grams). This results in a unit of degrees Celsius per gram (°C/g) or Kelvin per gram (K/g).

3. What is the significance of the temperature/gram ratio in chemistry?

The temperature/gram ratio is significant because it allows scientists to compare the specific heat capacities of different substances. It also helps to determine the amount of heat energy required to cause a specific temperature change in a substance.

4. How is the temperature/gram ratio used in experiments?

The temperature/gram ratio is used in experiments by measuring the change in temperature of a substance and its mass, and then calculating the ratio. This information is then used to determine the specific heat capacity of the substance.

5. What are some practical applications of using the temperature/gram ratio in chemistry?

The temperature/gram ratio has many practical applications in chemistry, including determining the specific heat capacities of materials used in construction, calculating the amount of heat energy needed for industrial processes, and understanding the thermodynamics of chemical reactions.

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