Cody wanted to know how much heat was released from a reaction of steel wool and vinegar. He placed a thermometer inside a cup that held the steel wool and vinegar. He must decide whether to leave the cup open, as shown with Cup 1, or to cover the cup, as shown with Cup 2.

Which design would control the variables in this experiment to ensure accurate
temperature readings?
A) Cup 1. The thermometer can be read more accurately.
B) Cup 1. It will not trap the heat and alter the temperature readings.
C) Cup 2. The cover will control for any loss of heat from the top of the cup.
D) Cup 2. It will prevent fumes from escaping into the air.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

a pan containing water is placed in a positio n where it is exposed to a 10 mile per hour wind. the pan contains a uniform depth of 1.27 cm of water, is quite wide, and has a length of 2.44 m in the wind direction. the water in the pan is at a constant temperature of 15.5 °c.

wher is the rest of the question