Answer:
ΔU = 25.8 J
Explanation:
The gas absorbs 33.3 J of heat, that is, Q = 33.3 J.
The work (W) of expansion can be calculated using the following expression:
W = -P. ΔV
where,
P is the external pressure
ΔV is the change in volume
W = -1.45 × 10⁴ N . m⁻² × (8.40 × 10⁻⁴ m³ - 3.24 × 10⁻⁴ m³) = -7.48 J
The change in the internal energy (ΔU) is:
ΔU = Q + W
ΔU = 33.3 J + (-7.48 J) = 25.8 J
The chalk particles embed themselves into the small pores on the surface.
Although a chalkboard seems smooth to the touch, it is quite rough at the microscopic level, with <em>pores</em> that reach below the surface.
When you drag chalk across the board, friction causes small particles of chalk to rub off onto the surface.
If you leave the markings for a long time, some of the chalk particles will work their way into the pores.
A brush will remove the surface particles, but <em>it will not be able to get at the particles in the pores</em>.
Because fluorine has a higher electronegativity
Answer:
An Educated Guess
Explanation:
After the scientist is done with the experiment he should do an educated guess, they use the data from the experiments to make charts and graphs to communicate the results of the experiment. After the scientists makes the hypothesis, they perform this procedure.
Answer: 
kJ
Explanation:
The thermochemical equation for decomposition of ammonium nitrate is:
Given mass= 50.0 kg =
(1kg=1000g)
According to stoichiometry:
1 mole of 
gives = 82.1 kJ of heat
Thus 
of give =
kJ of heat
Thus kJ of heat is evolved from the decomposition of 50.0 kg of ammonium nitrate.
