Answer:
The pressure of the gas increased (if temperature remained constant).
The Boyle's law supports this observation.
Explanation:
The initial measurements of the gas are given as;
volume = 100 L
Pressure = 300 kpa
The second measurement is given as;
Volume = 75 L
The second reading implies that the volume of the gas has decreased. If the temperature of the gas remained constant, then the pressure must have increased according to the Boyle's law;
At constant temperature, the pressure of a given mass of an ideal gas is inversely proportional to its volume.
 
        
             
        
        
        
Answer:
C. two atoms of oxygen.
Explanation:
Step 1: Data given 
Silicon has 14 electrons
Silicon is part of Group IV, all the elements there have 4 valence electrons.
It can form a compound when 4 valence electrons bind with the 4 valence elctrons of silicon
A. four atoms of calcium.
Calcium has 2 valence elctrons. 4 atoms of calcium <u>cannot bind</u> on 1 atom of silicon since there are only 4 valence electrons. 
B. one atom of chlorine.
1 atom of chlorine has 7 valence electrons. Chlorine can bind with an atom with 1 valence electron. Since silicon has 4 valence electrons, they will <u>not bind.</u>
Silicon can bind with 4 atoms of chlorine to form SiCl4
C. two atoms of oxygen.
Oxygen has 6 valence electrons, this means oxygen can bind with an element with 2 valence electrons.
Since silicon has 4 valence electrons, it <u>can bind</u> with 2 atoms of oxygen to form SiO2 (silicon dioxide).
D. three atoms of hydrogen.
Hydrogen has 1 valence electron. 1 hydrogen atom can bind with an element that has 7 valence electrons.
Three atoms of hydrogen can bind with an element that has 5 valence electrons.
Silicon <u>will not</u> bind with 3 atoms of hydrogen ( but can bind with 4 atoms of hydrogen)
 
        
             
        
        
        
Answer: B. triH sol Mgl2= -triHlat+ triHhydr Mg^2+ 2triHhydr^l-
Explanation:
Just did it and it was right
 
        
             
        
        
        
 Your question looks a bit incomplete as you have the same contents in options a) and d). According to your list, I can't see the correct answer, but I can give you one.The difference between the potential energy of the products of the potential energy of the reactants is equal to the enthalpy of the reaction.