Given:
Half life(t^ 1/2) :30 years
A0( initial mass of the substance): 200 mg.
Now we know that
A= A0/ [2 ^ (t/√t)]
Where A is the mass that remains after t years.
A0 is the initial mass
t is the time
t^1/2 is the half life
Substituting the given values in the above equation we get
A= [200/ 2^(t/30) ] mg
Thus the mass remaining after t years is [200/ 2^(t/30) ] mg
Answer:
A. The object broke apart and seemed to disappear when dropped into the glass of water.
Explanation:
In a physical change, the physical properties of the matter usually the state of the matter is altered. Most physical changes are usually reversible and does not lead to the production of new substances.
When the solid object was dropped into the water beaker and it dissolves by disappearing the solution, we have experienced a physical change. This is a dissolution reaction. If we heat the solution and water given off, we can recover back the dissolved solid object.
Answer: 26.8 kJ of energy is needed to vaporize 75.0 g of diethyl ether
Explanation:
First we have to calculate the moles of diethyl ether
As, 1 mole of diethyl ether require heat = 26.5 kJ
So, 1.01 moles of diethyl ether require heat = 
Thus 26.8 kJ of energy is needed to vaporize 75.0 g of diethyl ether
