<u>Answer:</u>
<em>The amount of energy needed when water at 72 degrees c freezes completely at 0 degrees c is 
Joules</em>
<em></em>
<u>Explanation:</u>
where
= Final T - Initial T
=30125J
Q is the heat energy in Joules
c is the specific heat capacity (for water 1.0 cal/(g℃)) or 4.184 J/(g℃)
m is the mass of water
mass of water is assumed as 100 g (since not mentioned)
is the heat energy required for the phase change
=mass × heat of fusion
Total heat = 
Total Heat = 30123J + 33600J
= 63725 J
= Joules is the answer
Decantation
Centrifugation
Filtration
Evaporation
Answer:
a
Explanation:
the solution is extremely acidic and will dissolve the zinc rod
The molarity of a solution equals to the mole number of the solute/the volume of the solution. For NH4Br, we know that the mole mass is 98. So the molarity is (14/98) mol /0.15 L=0.95 mol/L.
Answer:
It takes 1,068.76 grams of nitrogen to fill an 855 L tank at STP.
Explanation:
The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C or 273.15 °K are used and are reference values for gases.
On the other side, the pressure, P, the temperature, T, and the volume, V, of an ideal gas, are related by a simple formula called the ideal gas law:
P*V = n*R*T
where P is the gas pressure, V is the volume that occupies, T is its temperature, R is the ideal gas constant, and n is the number of moles of the gas.
So, in this case:
- P= 1 atm
- V= 855 L
- n= ?
- R= 0.082
- T= 273.15 K
Replacing:
1 atm* 855 L= n* 0.082 * 273.15 K
Solving:
n= 38.17 moles
Being the molar mass of nitrogen N2 equal to 28 g / mol, you can apply the following rule of three: if there are 28 grams in 1 mole, how much mass is there in 38.17 moles?
mass= 1,068.76 grams
<u><em>
It takes 1,068.76 grams of nitrogen to fill an 855 L tank at STP.</em></u>
