Answer:
Rock Y
Explanation:
The rock that is older shall be determined based on the number of half lives it has witnessed. A half life is simply the amount of time required for a sample to decay to half of its original mass.
Rock X
From 100% uranium, it decays to 50% uranium. This means it went through just one half life.
Rock Y
From 100% uranium to 25% uranium
100 --> 50 (first half life)
50 --> 25 (second half life)
This means it wen through 2 half lives.
Rock Y is older than Rock X
Answer:
Calcium
Explanation:
It has 20 electrons to start, loses two to become Ca 2+, and is left with 18 electrons
I think the correct answer from the choices listed above is the first option. The Greeks were the first to use the term atom. In 450 BCE, Democritus coined the term átomos which means "uncuttable" or "the smallest indivisible particle of matter".
Answer:
1.71 kJ/mol
Explanation:
The expression for the calculation of the enthalpy change of a process is shown below as:-
Where,
is the enthalpy change
m is the mass
C is the specific heat capacity
is the temperature change
Thus, given that:-
Mass of CaO = 1.045 g
Specific heat = 4.18 J/g°C
So,
Also, 1 J = 0.001 kJ
So,
Also, Molar mass of CaO = 56.0774 g/mol
Thus, Enthalpy change in kJ/mol is:-
