1-When gaseous water absorbs sufficient heat , it decomposes into its elements , as shown below . 2 H₂O ( g ) → 11₂ ( 9

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1-When gaseous water absorbs sufficient heat , it decomposes into its elements , as shown below . 2 H₂O ( g ) → 11₂ ( 9 ) + O₂ ( g ) AH = 242 kJ If 255 kJ are absorbed by a given amount of water vapor , up to how many moles of oxygen gas can be liberated ?
2- Methanol , CH3OH , is a fuel additive for some combustion engines . How much heat , in kJ , are released when 3.98 mL of methanol is combusted in the presence of oxygen gas ? The density of methanol is 0.792 g / mL CH3OH ( 1 ) +302 ( 9 ) → CO₂ ( g ) + 2 H₂O ( g ) AH - 638.6 kJ
3- A mercury " mirror " can form inside a test tube when mercury ( II ) oxide , HgO ( s ) , thermally decomposes as shown in the equation below . 2 HgO ( s ) 2 Hg ( 1 ) + O2 ( 9 ) AH 181.6 kJ How many joules of heat are needed to convert 0.860 moles of mercury ( II ) oxide to liquid mercury ?
4- When barium hydroxide , Ba ( OH ) 2 , reacts with ammonium chloride , NH4CI , a highly endothermic reaction takes place . Ba ( OH ) , ( aq ) + NH , Cl ( s ) → BaCl2 ( aq ) + 2H , O ( l ) + 2NH3 ( g ) AH = 90.7 kJ How many moles of barium hydroxide , are needed to absorb 52.2 kJ of heat from the environment from the equation above ?
5- The reactions of nitrogen oxides are important in the environment and in industrial processes . Calculate the heat transferred , in kJ , when 243 g of NO gas reacts with excess oxygen to form solid dinitrogen pentoxide . 4 NO ( g ) + O₂ ( g ) → 2 N₂O5 ( s ) AH - 219 kJ
6- How many kilojoules of heat would be required to fully melt a 0.834 m³ block of ice , provided that the density of ice is 917 kg / m³ ? H₂O ( s ) → H₂O ( 1 ) AH = 6.01 kJ