Designing a Hand Warmer Report Sheet Name ______________________________ Partner’s Name _____________________ 1. Report the experimentally determined ΔH expressed per mole of solute and per gram of solute below. Show calculations for your assigned solutes. Share data with your team. Who tested Solute Molar ΔH ΔH the solute? Mass (kJ/mol) (kJ/g) (g/mol) NH4NO3 CaCl2 LiCl NaCH3CO2 Na2CO3 NaCl 2. Calculate, for each solid, the temperature change that would result if 10. grams of solid were dissolved in 40. g of water. Show calculations Include the sign (positive or negative). Solute ΔT (°C) NH4NO3 CaCl2 LiCl NaCH3CO2 Na2CO3 NaCl Designing a Hand Warmer Report Sheet Name ______________________________ Partner’s Name _____________________ 3. Look up the solubility of each solid at 20 °C. Use this information to calculate how much of each solute can dissolve at room temperature (20 °C) in 40. mL of water. Show one sample calculation. Solute Solubility Solubility in 40 g (g per 100 g water) water (g) NH4NO3 CaCl2 LiCl NaCH3CO2 Na2CO3 NaCl 4. View the MSDS (material safety data sheets) sheets for each of the solutes. MSDS sheets can be found on line at http://www.flinnsci.com/msds-­‐search.aspx? Summarize BRIEFLY findings below. Solute Safety Concerns NH4NO3 CaCl2 LiCl NaCH3CO2 Na2CO3 NaCl Designing a Hand Warmer Report Sheet Name ______________________________ Partner’s Name _____________________ 5. Calculate % error in molar enthalpy of solution for each. Show one sample calculation. Solute ΔH (kJ/mole) % error 6.
NH4NO3 + 25.41 kJ/mol
CaCl2 - 120 kJ/mol LiCl - 37.1 kJ/mol NaCH3CO2 - 17.3 kJ/mol
Na2CO3 - 28.1 kJ/mol
NaCl +3.9 kJ/mol Suggest sources of error that would explain the percent error above. 7. Suggest one way the experiment could have been improved. 8. a. Which solid is the best choice considering effectiveness, safety, and cost? ______________________________________________________________________________ b. Justify your choice on the back. Be concise!! Designing a Hand Warmer Report Sheet Name ______________________________ Partner’s Name _____________________ 9. Instant cold packs are used to treat sports and other injuries when ice is unavailable. Research the properties of commercial cold packs and select a “cold pack solid’ from among the solids you tested in this activity. Propose a design (including quantity of solid and volume of water) for an effective instant cold pack. Make a labeled sketch of your design.