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

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 kl, is absorbed or released?

A) Exothermic

B) (1) -410.5 kJ  (2) -98.1 kcal

C) -976.44 kJ

Explanation:

A) By the value of ΔH (-1236 kJ), we can see that it's negative, it means that the heat is being lost by the reaction, and, because of that, the reaction is exothermic.

B) The molar mass of ethanol is 46.07 g/mol, so, at 15.3 grams, the number of moles is:

n = mass/molar mass

n = 15.3/46.07

n = 0.3321 mol

By the equation

1 mol of ethanol           -1236 kJ

0.3321 mol of ethanol x

By a simple direct three rule:

x = -410.5 kJ

1 kJ 0.2390 kcal

-410 kJ y

y = -98.10 kcal

C) The molar mass of water is 18 g/mol, so the number of moles at 42.7 g is:

n = 42.7/18

n = 2.37 moles

By the equation

3 moles of water     -1236 kJ

2.37 moles of water x

By a simple direct three rule:

3x = -2929.32

x = -976.44 kJ

for step 7 table c on the lab "newtons law of action"   the average time it took the car to travel .25 meters   was 1.92 seconds.

the average time it took the car to travel 0.50 meters was 2.61 seconds

hope this : )

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.