The thermite reaction demonstrated in class requires high temperatures to start the reaction. A simple open flame is not enough to start the reaction. Once the reaction is going, then it generates enough heat to keep the reaction going. According to the literature on thermite, it takes temperatures of about 2200 C to start the reaction. If you need to heat up one gram of thermite (assumed to be 25% aluminum metal and 75% iron oxide) to start the reaction, then how many joules of heat must the ignition system provide? Assume the heat capacity of aluminum is 0.90 J/g-K and iron oxide is 0.45 J/g-K and that your thermite mixture starts at room temperature of 20 C. Ignore any enthalpy of phase changes that may occur in heating up the mixture.

1 g thermite--25% Al; 75% Fe2O3 makes

0.25g Al and 0.75g Fe2O3.

q = [mass Al x specific heat Al x (Tfinal-Tinitial)] + [mass Fe2O3 x specific heat Fe2O3 x (Tfinal-Tinitial)]
Substitute and solve for q.

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To calculate the amount of heat required to heat up one gram of thermite to start the reaction, we need to consider the heat capacity of both aluminum and iron oxide.

The equation for calculating the heat required is given by:

Q = m * Cp * ΔT

where:
Q = heat required (in joules)
m = mass of the substance (in grams)
Cp = heat capacity of the substance (in J/g-K)
ΔT = change in temperature (in K)

First, we need to calculate the change in temperature (ΔT). Since the initial temperature is 20 °C and we need to heat it to the ignition temperature of 2200 °C, the change in temperature will be:

ΔT = 2200 °C - 20 °C = 2180 K

Now, let's calculate the heat required for each component of the thermite mixture.

For aluminum:
m = 1 g
Cp = 0.90 J/g-K

Q_aluminum = m * Cp * ΔT

Q_aluminum = 1 g * 0.90 J/g-K * 2180 K

Q_aluminum = 1962 J

For iron oxide:
m = 1 g
Cp = 0.45 J/g-K

Q_iron_oxide = m * Cp * ΔT

Q_iron_oxide = 1 g * 0.45 J/g-K * 2180 K

Q_iron_oxide = 981 J

To find the total heat required, we sum up the heat required for aluminum and iron oxide:

Q_total = Q_aluminum + Q_iron_oxide

Q_total = 1962 J + 981 J

Q_total = 2943 J

Therefore, the ignition system must provide approximately 2943 joules of heat to heat up one gram of thermite to start the reaction.