Thermochemistry

Practice Problems: Use the values given on the previous page for solving these problems. 1 . Calculate the heat needed to raise 27.0 g of water from 10.0 .C to 90.0 .C. 2. How many kJ are required to heat 45.0 g of H20 at 25.0 C and then boil it all away? Energy! (45. 09) ( 4.18 5/gic ) ( 75" ( ) = 14107. 15 J = 14107. J energy = ( 45. 09 ) ( 2260 * g ) + 101 700 . 07 115808:5 JX KJ = 115. 80 BT KJ = 107 780 J TooOJ 120 kx 3. Calculate the amount of energy used when 33.3 grams of ice at 0.00 .C is converted to steam at 150.0 .C. 33. 39 ( 3 3 8 / J (9 ) = 11185.5 ( 3 3 . 39 ) ( 4 . 1845 / g'c ) (60 ( ) = 20 899.08 2 4. How many joules of heat are needed to change 50.0 grams of ice at -15.0 .C to steam at 120.0 .C? U. Calculate the number of joules given off when 32.0 grams of steam cools from 110.0 .C to ice at -40.0 .C. 6. How much energy is required to convert 100.0 g of water at 20.0 .C completely to steam at 100.0 .C? 7. What amount of ice must be added to 540.0 g of water at 25.0 .C to cool the water to 0.0 .C and have no ice 8. Consider the practice problem on the front and the calculated values for each step. Now look at the heating/cooling curve diagram in the upper right hand corner. What's wrong with this diagram