A small 45 g water sample A is heated for 243 seconds by a 20 Watt heater result
ID: 969872 • Letter: A
Question
A small 45 g water sample A is heated for 243 seconds by a 20 Watt heater resulting in an increase temperature capital delta T subscript A . The heated small water sample A is added to a larger tank of water, sample B, but, during the pouring process, water sample A cools down by 10% (a 10% decrease in the capital delta T subscript A ). The larger tank of water sample B was originally 349 g of water, before sample A was added. What is the final temperature change capital delta T subscript A plus B end subscript of the combined samples? Units are in degrees Celsius; do not include units in your answer. Use Cp = 4.1813 J/goC, and give your answer to two decimal places.
Explanation / Answer
20W =20 Joules/sec
243 seconds gives rise to 243*20 joules of heat= 4860 joules
heat added= mass* specific heat* (delT)A
(delT)A= 4860/ (45*4.18) =25.83
total mass after pouring = 349+45= 394 gms
new delT of water = 0.1*25.83= 2.583
Heat now remaining = 4860/(4.18*2.583)=450 Joules
450= 394*4.18* ( temperature dffference)
temperature difference= 450/394*4.18)=0.27 ( this is the temperature difference of combined sample)