What observations support the assumption that all of the iodine reacted with the zinc explain?

The appearance of white solid zinc iodide shows that a chemical reaction has taken place.

There are certain cues that show that a chemical reaction has occurred. Some of those cues include;

When iodine reacts with zinc, we see the appearance of white solid zinc iodide shows that a chemical reaction has taken place.

Learn more about chemical reaction: link

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

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the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.