Which of the following would be evidence that a chemical reaction has occurred? (Select all that apply.) *
a change in shape
a precipitate is formed
an unexpected change in color
the formation of gas bubbles
smoke begins to form
clear liquids remain clear
the odor changes
the substance becomes very cold

1) precipitate is formed

2) unexpected color change

3) formation of gas bubbles

4) smoke forms

5) odor change

6) substance becomes cold

Explanation:

1/3) its a new substance.

2/5) they are both changes to the original substance that cannot be reversed.

4) where theres smoke theres fire, and burning is classified as a type of chemical change.

6) it could possibly be an endothermic reaction, where it absorbs heat and the substance becomes cold.

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements

answer: the value of enthalpy change will be -152.80 kj.

solution:

pressure = 1atm , temperature = = 298 k

given that pressure and temperature are same in both gases , the number of moles of both gases can be determined by the ideal gas equation.

according to reaction 3 moles no are reacting with 1 mol of ,then 0.49 mol of no will react with moles of ozone that is 0.16 moles of ozone. since, no is limiting reagent and is an excessive reagent.

enthalpy change for the reaction between the given volumes of the gases is :