Ethanol is added to gasoline because the oxygen it contains improves gasoline's burning efficiency. Its combustion reaction is given below. CH3CH2OH(l) + 3O2(g) → 2CO2(g) + 3H2O(g) ∆H = - 1236 kJ a) Is this an exothermic or endothermic reaction? b) If 15.3 grams of pure ethanol is completely converted to products, calculate how much heat is absorbed or released, in: (1) kJ and in (2) kcal c) If 42.7 g of water vapor is produced, how much heat, in kJ, is absorbed or released?

A) The reaction is exothermic reaction

B) 46 gm CH3CH2OH  = 1236KJ

15.3 gm ch3ch2OH = 1236/46 x 15.3

= 411.10 KJreleased

therefore  1 KJ = 0.239 K cal

so, 411.10 x 0.239 kcal

= 98.2529 released

c) 54 gm of H2O produced = 1236KJ

so, 42.7 gm H2O produced = 1236/54 x 42.7KJ

= 977.35 KJ released.

Explanation:

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6