Heating and Cooling Curves Practice Problems

The graph below represents the heating curve of carbon disulfide (CS₂), a compound widely used in cellophane manufacturing.

At −50°C, is CS₂ solid, liquid, or gas?

Bagasse, a by-product in the sugarcane milling process, can be used as a fuel in steam production. If the combustion of 2.00 lbs of bagasse releases 1.95×10⁷ J heat, calculate the amount of bagasse (in kilograms) needed to convert 275 kg of water to steam. ΔH_vap, H2O = 2.26×10³ J/g

The combustion of 1.000 lb of dry firewood can provide an amount of 7.256×10⁶ J heat. If dry firewood is used in a boiler furnace, how many kilograms of dry firewood are needed to raise the temperature of 250.0 kg of water from 25.00°C to 100.0°C? Specific heat of water = 4.184 J/g•°C

Formic acid (CH₂O₂) is widely used in rubber industries as a coagulant agent. A sample of liquid CH₂O₂ with a temperature of 30.95°C was added to 30.50 g solid CH₂O₂ at a temperature of 8.300°C. After some time, all of the solids melted, and the temperature of the liquid dropped to 8.300°C. Using the following data: Melting point = 8.300°C, ΔH_fus, CH2O2 = 275.5 J/g, and c_{CH2O2, liq} = 2.151 J/g•°C, how many grams of liquid CH₂O₂ were in the sample?

Using the following values: ΔH_fus, NH3 = 332.3 J/g, c_{NH3, liq} = 4.744 J/g•°C, and ΔH_vap, NH3 = 1370 J/g, determine the amount of heat energy in kilojoules needed to convert a 50.00 g sample of solid ammonia at −77.73°C to liquid ammonia, heat the liquid to −33.33°C, and change the liquid to gas at −33.33°C.

Water at 40.00°C is used for maintaining a specified temperature of a chemical tank. The temperature of the water dropped to 32.50°C. If the water consumption is 5.000×10⁴ g, how many kilojoules of heat were transferred from the water? Specific heat of water = 4.184 J/g•°C

Consider a gas sample contained in a vessel at 600 K shown in figure (i). If the boiling point of the gas is 400 K, which figure (ii)-(iv) depicts the gas when the temperature is decreased from 600 K to 300 K? If the boiling point of the gas is 250 K, which figure represents the gas when the temperature is at 300 K?

Choose the correct statement about the heat of the vaporization of a liquid.

Calculate the energy involved in kJ in the conversion of 503 g of steam at 373 K to ice at 254 K

C_H2O(s) = 2.06 J/g.°C

C_H2O(l)  = 4.18 J/g.°C

C_H2O(g)  = 2.03 J/g.°C

ΔH_vap = 40.6 kJ/mol

ΔH_fus = 6.02 kJ/mol

Calculate the heat required in kJ for the phase change of 32.1 g of solid ethanol at -121°C to liquid ethanol at 0°C

Data for ethanol: 

T_f = -114°C

ΔH_fus = 5.02 kJ/mol

C_EtOH(s) = 0.97 J/g-K

C_EtOH(l)  = 2.3 J/g-K