Which of the following is an example of observational scientific investigation?
a. mixing two reactants together in a small beaker
b. noting the color of a solution when heated.
c. placing test tubes in an ice bath for 15 minutes
d. drying solid produced by placing it in an oven.

The correct answer will be option-B.

Explanation:

A scientific investigation involves many steps to answer and explain the natural phenomenon.  The observational scientific investigation is a way which includes making an observation which is also the first step of the scientific method.

In the given question, observing the color of the solution while heating will be considered as an example of observational investigation as it states that something has been observed with the senses of the human. All other are cases of experimental investigation.

Thus, Option-B is the correct answer.

"the periodic table is arranged in order of atomic number."

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"