Here we have to discuss the understanding of world through radiocarbon or uranium.
The radiocarbon or uranium helps us to determine the age of the world.
All uranium or radiocarbon elements after ejecting the radioactive rays convert to non-radioactive element lead (²⁰⁸Pb). If we assume that during the generation of world there were not any amount of lead was present i.e. only uranium or radiocarbon was present. Then by analysis of any uranium or radiocarbon at the present date one can determine the age of the world as follows:
In present moment we know that the ratio of uranium (U) and lead (Pb) in any uranium ore is 10:3 (gram atom ratio)
So, 
= 
Therefore, from the equation: ln
= λt (where λ = rate of dissociation of uranium, t = time); we can write:
t = λ⁻¹ ln = λ⁻¹ln
.
On plugging the dissociation rate of uranium we can obtain the age of the world, which is nearly 1.5×10⁹ years.
Thus the use of radioactive element to understand the world is explained.
Answer: 3. Mass is lost due to the conversion of mass to energy.
Answer: The correct statements are ; A and B.
Explanation:
The strength of the magnetic field(B) in an electromagnet can be calculated using formula:
= Relative permeability
N = number of turns
I = Current in the wire of the solenoid
L = length of the solenoid or electromagnetic
As we can see from the formula:
So, by increasing the turns and increasing current flowing through wire one can increase the strength of an electromagnet.
Hence, the correct statements are ; A and B.
Answer:
12.5 g of Li are needed in order toproduce 0.60 moles of Li₃N
Explanation:
The reaction is:
6Li(s) + N₂(g) → 2Li₃N(s)
If nitrogen is in excess, the lithium is the limiting reactant.
Ratio is 2:6
2 moles of nitride were produced by 6 moles of Li
Then, 0.6 moles of nitride were produced by (0.6 .6)/ 2 = 1.8 moles of Li
Let's convert the moles to mass → 1.8 mol . 6.94 g/ 1mol = 12.5 g of Li
Answer: A. To change the potential energy of the reactants.
Explanation:
Catalysts make such a breaking and rebuilding happen more efficiently. They do this by lowering the activation energy for the chemical reaction. Activation energy is the amount of energy needed to allow the chemical reaction to occur. The catalyst just changes the path to the new chemical partnership.
