Andrew has 20 rocks in his rock collection. He decides that he will select 2 rocks to add to his collection each time he goes to a river. He writes an equation that represents how many rocks, r, he will have after n number of trips to a river. Which statements are representative of the equation Andrew writes? Select all that apply.

Express the following number in scientific notation. 0.026890 =

Estimate the molar mass of the gas that effuses at 1.6 times the effusion rate of carbon dioxide.

Astudent pours 10.0 g of salt into a container of water and observes the amount of time it takes for the salt to dissolve. she then repeats the process using the same amounts of salt and water but this time she slowly stirs the mixture while it is dissolving. the student performs the experiment one more time but this time she stirs the mixture rapidly. the dependent variable in this experiment is: time for salt to dissolve speed of stirring amount of water mass of salt