4. When backpacking in the wilderness, hikers often boil water to sterilize it for drinking. Suppose that you are planning a backpacking trip and will need to boil 35.0 L of water for your group. What volume of fuel should you bring? Assume that the fuel has an average formula of CH16; 15% of the heat generated from combustion goes to heat the water (the rest is lost to surroundings); the density of the fuel is 0.78 g/ml; the initial temperature of the water is 25.0 °C; and the standard enthalpy of formation of CH16 is -224.4 kJ/mol.

A 21 gram piece of metal at 125 oC is dropped into 87 grams of water at 17 oC. The water temperature rose to 38 oC. Calculate the heat change of the metal in Joules. (DO NOT PUT UNITS IN YOUR ANSWER.) Assume that all of the heat lost by the metal is transferred to the water and no heat is lost to the surroundings. The specific heat of water is 4.184 J/g oC.

1 A piece of metal with a specific heat of 1.011 J/gºC is heated to 123.1ºC and then placed in 111.031 g of water which is at a temperature of 3.6 ºC. After a minute, the temperature of the water has stopped changing and is now 55.8ºC. Assuming that there are no heat losses to the container or surroundings, what is the mass of the piece of metal in grams? Assume that water has a specific heat of 4.184 J/gºC. Enter your answer with at least 3 sig figs.

6) A block of rhenium metal (specific heat =0.0329 cal/ gC) is heated to 88.2C and then dropped into 100.0 g of water initially at 26.4 C. The final temperature of the mixture is 32.4C. What was the mass of the block of rhenium?

8. Instant cold packs can be made from ammonium nitrate by mixing/reacting it with water (reaction shown below). When 1.25 g of NH4NO3 is dissolved in 25.0 g of water at 25.8 °C, the temperature of the water after the reaction is 21.9 °C. What is the enthalpy change (ΔH) for this reaction in units of kJ/mol of NH4NO3? The heat capacity of water is 4.18 ?/ ?℃ . NH4NO3(s)  → NH4+(aq) + ??3 − (aq)

1. A thermometer placed in a solution undergoing a chemical reaction indicates an increase in temperature as the reaction proceeds. Is this reaction endothermic or exothermic? Describe if heat energy is lost or gained from the reaction (the system) to the surroundings. What is the sign of the enthalpy change (AH) of this reaction? 2. A student performs a reaction and determines the enthalpy change (AH) to be 31.4 kJ. Will the temperature of the surrounding solution increase or decrease as a result of this chemical process? 3. If you hold 3 grams of ice in your hand at room temperature, your hand will become cold. a) Is the reaction H,O(s) – H,O(1) endothermic or exothermic? b) In which direction does heat flow?

In order to break water into hydrogen and oxygen, water is heated to more than 500°C. Which kind of reaction is this and why? It is exothermic because heat needs to be released by the reactants to form the products. It is endothermic because heat needs to be released by the reactants to form the products It is exothermic because heat needs to be absorbed by the reactants to form the products. It is endothermic because heat needs to be absorbed by the reactants to form the products.

Suppose a boil water notice is sent out advising all residents in the area to boil their water before drinking it or using it for cooking. You need to boil 18.0 L of water using your natural gas (primarily methane) stove. What volume of natural gas is needed to boil the water if only 10.1% of the heat generated goes towards heating the water. Assume the density of methane is 0.668 g/L, the density of water is 1.00 g/mL, and that the water has an initial temperature of 21.4 °C. Enthalpy of formation values can be found in this table. Assume that gaseous water is formed in the combustion of methane.

3. A piece of metal weighing 59.047 g was heated to 100.0 °C and then put it into 100.0 mL of water (initially at 23.7 °C). The metal and water were allowed to come to an equilibrium temperature, determined to be 27.8 °C. Assuming no heat lost to the environment, calculate the specific heat of the metal.

A piece of metal with a specific heat of 1.153 J/gºC is heated to 124.6ºC and then placed in 120.382 g of water which is at a temperature of 2.1 ºC.  After a minute, the temperature of the water has stopped changing and is now 45.5ºC.   Assuming that there are no heat losses to the container or surroundings, what is the mass of the piece of metal in grams? Assume that water has a specific heat of 4.184 J/gºC. Enter your answer with at least 3 sig figs.