Instant cold packs, often used to ice athletic injuries on the field, contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves according to the following endothermic reaction: NH4NO3(s)→NH4+(aq)+NO3−(aq)NH4NO3(s)→NH4+(aq)+NO3−(aq) In order to measure the enthalpy change for this reaction, 1.35 gg of NH4NO3NH4NO3 is dissolved in enough water to make 20.5 mLmL of solution. The initial temperature is 24.5 ∘C∘C and the final temperature (after the solid dissolves) is 20.0 ∘C∘C.     Calculate the change in enthalpy for the reaction in kJkJ. (Use 1.0gmL−11.0gmL−1 as the density of the solution and 4.184Jg−1∘C−14.184Jg−1∘C−1 as the specific heat capacity.) Express your answer to two significant figures and include the appropriate units.

a Balance the following chemical equation: ZnCl₂ (aq) + NaOH(aq) → Zn(OH)2 (s) + NaCl(aq) 2ZnCl₂ (aq) + 3NaOH(aq) → 4Zn(OH)2 (s) + 3NaCl(aq) 3ZnCl₂ (aq) + NaOH(aq) → 4Zn(OH)2 (s) + 2NaCl(aq) ZnCl₂ (aq) + 2NaOH(aq) → Zn(OH)2 (s) + 2NaCl(aq) ZnCl₂ (aq) + 3NaOH(aq) → Zn(OH)2 (s) + 3NaCl(aq) b Balance the following chemical equation: Ba(C₂H3O2)2 (aq) + K₂SO4 (aq) → BaSO4(s) + KC2H3O2 (aq) 2Ba(C₂H3 O2)2 (aq) + 5K2SO4 (aq) → 2BaSO4(s) + 2KC2H3O2 (aq) 2Ba(C₂H3 O2)2 (aq) + 2K2SO4 (aq) → 2BaSO4(s) + 3KC₂ H3 O2 (aq) Ba(C₂H3O2)2 (aq) + K₂SO4 (aq) → BaSO4 (s) + 2KC₂H3O2 (aq) Ba(C2₂H3 O2)2 (aq) + 4K₂SO4 (aq) → BaSO4(s) + KC₂ H3O₂ (aq) C Balance the following chemical equation: SO₂(g) + H₂O(1) → H₂SO3(aq) 3SO₂(g) + H₂O(1) → 4H₂SO3(aq) SO₂(g) + 2H₂O(1) → 2H₂SO3(aq) 2SO2(g) + 3H₂O(1) → 6H₂SO3(aq) SO₂(g) + H₂O(1) → H₂SO3(aq)

Which one of the following reactions would produce a gas?     Na2SO3(aq) + Ba(OH)2(aq) →     None of these reactions would produce a gas     CuSO4(aq) + K2S(aq) →     NaHSO3(aq) + HNO3(aq) →      HClO4(aq) + Na2SO4(aq) →

Which one of the following represents a combination reaction?   C2H4(g) + H2(g) → C2H6(g)       Fe(NO3)2(aq) + Na2S(aq) → FeS(s) + 2 NaNO3(aq)       Cr(s) + Pb(NO3)2(aq) → Cr(NO3)3(aq) + Pb(s)       2 KClO3(s) → 2 KCl(s) + 3 O2(g)