calcium oxide has been proposed as a substance. calculate the minimum mass of CaO that would be required to cause this temperature change

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Calcium oxide, , has been proposed as a substance that can be used to heat water quickly for portable heating packs or for cooking. When placed in water, reacts as shown by hte equation below:

⇄

a) A student wants to design a heating pad that could heat a 150.0 g sample of water from 25.0°C to 60.0°C.

(i) Calculate the amount of heat, in joules, that the water must absorb for its temperature to change by this amount. (Assume that specific heat capacity of water is 4.18J/(g.°C).)

(ii) Calculate the minimum mass of that the student would need to use in order to cause this temperature change.

(i) Q = 21,945J

              (ii) m = 467.87g

Explanation: Energy necessary for the water to absorb to heat up is calculated by:

Q is heat

c is specific heat capacity, in this case in J/g.°C

is change in temperature

(i) Calculating amount of heat:

Q = 21945J

The water needs 21,945 joules to increase by that amount of temperature.

(ii) According to the chemical equation:

⇄

it is needed 1 mol of each reagent to produce 1 mol of product.

Molar mass of water is 18g/mol. For 150g, there are:

n =

n = 8.34 mols

Molar mass of CaO is 56.1g/mol. For 8.34 mols:

m = 8.34*56.1

m = 467.87g

For calcium oxide to increase temperature in 35°C, the minimum necessary is 467.87 grams.

35. a insulated cylinder of solid gold (k 310 kw/m-k) of radius v2 m and height 5 m is heated at one end until the temperature at each point in the cylinder is given by w(r, y, z) (30 z2)(2-(r2+ y2). determine the rate of heat flow across each horizontal disk given by z 1, z 2, and z 3, identifying which has the greatest rate of heat flow across it.

explanation: