Calcium reacts with O2(g) to give calcium oxide, CaO. A sample of calcium of mas

Question

Calcium reacts with O2(g) to give calcium oxide, CaO. A sample of calcium of mass 1.00g is reacted with excess oxygen in a calorimeter containing 1000g of water and the following observations are made:

Specific heat capacity of water: 4.184 J g^-1 C^-1

Heat capacity of calorimeter: 50 J C^-1

Initial Temperature: 22.50 C

Final Temperature: 26.25 C

What is the value of Delta Hf for CaO in KJ mol^-1?

Calcium react with O2(g) to give calcium oxide. CaO. A s ample of calcium of mass 1.00g is reacted with excess oxygen in a calorimeter containing 1000g of water and the following observations are made: specific heat capacity of water: 4.184 Jg^-1 C^-1 heat capacity of calorimeter: 50 J C^-1 initial temperature: 22.50 C final temperature: 26.25 C what is the value of delta hf for CaO in KJ mol^-1?

Explanation / Answer

qsolution + qcalorimeter = qreaction

qsolution =(specific heat)solution ×masssolution ×delta Tsolution

qsolution= 4.184J/gc × (1gCa + 1000gwater) × (26.25-22.50)C

qsolution =4.184 ×1001× 3.75J

qsolution = 15705.69J = 1.57 × 104J

qcalorimeter = (heat capacity)calorimeter × delta Tcalorimeter

qcalorimeter = 50J/C × (26.25-22.50)C

qcalorimeter = 187.5J = 0.0187 × 104J

qreaction  = 1.57× 104J + 0.0187 × 104J

qreaction = 1.589 × 104J

Delta Hf = -1.589 × 104J = -15.89kJ

moles of CaO

Ca +O2-----> CaO

1 mole of O2 reacts with 1 mole of Ca to give 1 mole of CaO

mole of Ca = 1g/140 = 0.025

so,moles of CaO = 0.025

DeltaHf per mole of CaO = -15.89/0.025 = -635.6kJ

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