How many grams of o2 are required to burn 18 grams of c5h12?
c5h12 + 8o2  5co2 + 6h2o

63,86 g O2  

Explanation:

You will first find the molecular weight (MW) of C5H12 and O2 with help of a periodic table.

Then C= 12,011 , H=1,008  y O=15,999      

So:  

C5H12 = 12,011*5 + 1,008*12      

MW =72,151 g/ mol C5H12      

O2 = 15,999*2      

MW = 31,998 g/ mol O2    

Use the equation to know that 1 mol C5H12 equals 8 mol O2    

Now you will start with the data of 18  grams of C5H12 and you obtain:      

18 g C5H12 x 1 mol C5H12     x 8 mol O2    x   31,998 g O2  = 63,86 g O2                                                    .                     72,151 g C5H12    1 mol C5H12      1 mol O2  

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.