In which type of reaction can two compounds exchange ions to form two different compounds?

Stoichiometry- i need with 14 and 15! an explanation would be appreciated!

An experiment is conducted to see if cats preferred skim milk or 2% milk. a cup of skim milkwas put out for 5 kittens and then measured how much the kittens drank over the course of aday. following a cup of 2% milk was purout for the skittens and then masured how much thekittens drank over the course of a day. the same kittens were used and the milk was served atthe same temperature. it was discovered that the cats liked the 2% milk more than the skimmilk. what is the dependent variable in this experiment?

How many moles of sulfur dioxide are in 2.26 × 10^33 sulfur dioxide molecules?