calcium oxide and water to produce calcium hydroxide and generate heat

# Calcium oxide and water to produce calcium hydroxide

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calcium oxide and water to produce calcium hydroxide and generate heat according to the reaction: CaO ( s )+ H 2 O ( l ) →Ca ( OH ) 2 ( aq ) ΔH = -82 kJ/mol a) Assuming that the heat capacity for coffee is the same as that of water, 4.18 Jg-1K-1 , calculate the energy needed to warm 210 cm3 of coffee by 40 °C. ΔT = 40 C × ( 1 K / 1 C )= 40 K c = 4.18 J / g K m = 210 c m 3 × ( 1 g / 1 c m 3 )= 210 g q ( can )= mc ΔT q ( can )=( 210 g ) × ( 4.18 J / g K ) × ( 40 K ) q ( can )= 35,112 J q ( can )= 3.5 10 4 J or 35 kJ b) Use this value to hence calculate the minimum mass of CaO in the can for it to function as specified. q ( can )= 35 kJ q ( 1 molof CaO )= 82 kJ n CaO = 35 kJ × 82 kJ / mol n CaO = 0.43 mol CaO m CaO = 0.43 mol× ( 56.07 g CaO / mol ) m CaO = 24.1101 g CaO m CaO = 24 g CaO

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Task: Design a product that can cool 100 cm3 of drinkable water by 5 °C in less than 5 minutes using one of the following chemicals: ammonium chloride (NH4Cl); solubility 37.2 g / 100 g water, \$62.40 per 500 g ammonium nitrate (NH4NO3); solubility 192 g / 100 g water, \$64.62 per 500 g *The dissolution of either of these compounds is endothermic and will absorb energy (heat) from the water surrounding it. Materials: - ammonium chloride (NH4Cl) - accurate thermometer - styrofoam “coffee cup” calorimeter - 250mL beaker - 50mL graduated cylinder - 100 mL distilled water - stirring rod - LabQuest 2 system - lab coat - safety glasses - gloves Problem: determine the minimum quantity of salt that can be dissolved in water to absorb thermal energy from surrounding water in the can (calorimeter).
• Fall '14
• Pell, Wendy

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