Heat Stoichiometry Review Quiz Heat = mass x ΔT x specific heat For each reaction write the balanced chemical equation including the energy term, and indicate whether the reaction is endothermic or exothermic. 1 (A) When 9.36 g of sodium carbonate reacts with an excess of hydrochloric acid, 2.22 KJ of heat are released. 1 (B) When 2.00 g of ammonium nitrate is dissolved in 50.00 ml of water, the temperature of the solution decreases from 25.58oC to 22.34oC.
Heat Stoichiometry Review Quiz Heat = mass x ΔT x specific heat For each reaction write the balanced chemical equation including the energy term, and indicate whether the reaction is endothermic or exothermic. 2(A) When 2.50 g of magnesium chloride is dissolved in 25.00 ml of water, the temperature of the solution increases from 21.00oC to 24.70oC. 2(B) 34.4 KJ are needed for 82.3 g of mercury (II) oxide to decompose into its component elements.
When 9.36 g of sodium carbonate reacts with an excess of hydrochloric acid 2.45 KJ of heat are released. 1mole Na2CO3 = 106 g = 9.36 g x KJ x KJ 2.45 KJ x = 27.7 KJ Exothermic Na2CO3 + 2 HCl → H2O + CO2 + 2NaCl + 27.7 KJ
0.677 KJ = 27.1 KJ / mole Endothermic 0.025 mole When 2.00 g of ammonium nitrate is dissolved in 50.00 ml of water, the temperature of the solution decreases from 25.58oC to 22.34oC. Heat = 50.00 g x 3.24 oC x 4.18 J/goC = 677 J 2.00 g NH4NO3 x 1 mole = 0.025 mole 80.0g 0.677 KJ = 27.1 KJ / mole Endothermic 0.025 mole 27.1 KJ + NH4NO3 → (NH4)1+ + (NO3)1-
Exothermic MgCl2 → Mg2+ + 2 Cl1- + 14.8 KJ When 2.50 g of magnesium chloride is dissolved in 25.00 ml of water, the temperature of the solution increases from 21.00oC to 24.70oC. Heat = 25.00 g x 3.70 oC x 4.18 J/g oC = 387 J 2.50g MgCl2 x 1mole = 0.0262 mole 95.3g 0.387 KJ 0.0262 mole = 14.8 KJ / mole Exothermic MgCl2 → Mg2+ + 2 Cl1- + 14.8 KJ
34.4 KJ are needed for 82.3 g of mercury (II) oxide to decompose into its component elements. x KJ = x KJ = 34.4 kJ x = 90.5 KJ 1 mole 216.6g HgO 82.3g Endothermic 181 KJ + 2HgO → 2 Hg + O2