The answer is C . when the light slows down
You would have to look for the mass of the sample and the volume of the sample.
The molecular weight is the same as molecular mass. You find this by using the periodic table
The molar mass of Mg(NO3)2 is 148.3
Answer: The bond formed between the elements will be ionic bond.
Explanation: We are given two elements having electronic configurations:
Element 1: 
Element 2: 
Element 1 can easily loose 1 electron to attain stable electronic configuration and Element 2 can accept 1 electron to attain stable electronic configuration.
For these elements, there will be a complete transfer of electron from Element 1 to Element 2. Hence, this will form a ionic bond.
From the configuration, Element 1 is Lithium and Element 2 is Fluoride. So, the compound is LiF.
Answer: 82.0 g/mole
Explanation:
Use the units to see that if we divide 1.64 grams by 0.0200 moles, we'll get a number that is grams/mole, the definition of formula mass.
1.64/0.0200 = 82.0 g/mole (3 sig figs)
We can't tell from this alone what the molecular formula might be, but C6H10 (cyclohexene) comes close (82.1 grams/mole).