To calculate the time it will take for all of the water to freeze, we first need to determine the amount of heat energy required to freeze the water.
The heat energy required to freeze water is 80 cal/g.
800 g of water x 80 cal/g = 64000 cal
Next, we will determine how long it will take to freeze the water by dividing the total amount of heat energy by the rate at which heat is being removed.
64000 cal ÷ 15 cal/s = 4266.67 s
Finally, we will convert the time from seconds to minutes.
4266.67 s ÷ 60 s/min = 71.11 min
Therefore, it will take approximately 71.11 minutes for all of the water in the ice cube tray to freeze.