Answer: mole
A formula unit represents the simplest ratio of elements in a mole of an ionic compound.
Explanation:
The formula unit, also known as the empirical formula, gives the simplest whole number ratio of the components of the elements in a mole of an ionic compound.
Thus, the formula unit and the molecular formula of a compound can be the same.
For example: Glucose with C6H12O6 will have a formula unit of CH2O. Thus, the simplest ratio of carbon, hydrogen and oxygen in glucose is 1:2:1
When you are doing a experiment, you are testing if your hypothesis is correct or false. If your hypothesis is false, you have to disgard it. If it is correct, you have to do many more parallels, and if they also confirm your hypothesis, your hypothesis can become a theory.
Answer : The initial temperature of system 2 is, 
Explanation :
In this problem we assumed that the total energy of the combined systems remains constant.
The mass remains same.
where,
= heat capacity of system 1 = 19.9 J/mole.K
= heat capacity of system 2 = 28.2 J/mole.K
= final temperature of system = 
= initial temperature of system 1 = 
= initial temperature of system 2 = ?
Now put all the given values in the above formula, we get
Therefore, the initial temperature of system 2 is,
As we know that
P.E. = mgh
where,
P.E. = Potential energy of the object =?
m= mass of object= 3kg
g= acceleration due to gravity = 9.8 ms^-2
h = height between object and animal = 0 m
Then
P.E. = 3× 9.8 × 0 = 0 Joules or 0J
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