Amount of Niobium-91 initially
= 300/91 =3.2967mol
2040 years = 3 ×680 = 3 half-lives
therefore, amount left = 0.4121mol
mass of Niobium-91 remaining = 0.4121 ×91 =37.5g
Answer:
41264 g of CO₂
Explanation:
Combustion reaction is:
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O
1 mol of propane react to 5 moles of oxygen in order to proudce 3 moles of carbon dioxide and 4 moles of water.
In a combustion reaction, our reactant reacts to oxygen and the products are always CO₂ and water.
We have the volume of propane but we need moles of it, so we need to apply density.
Density = mass / volume so mass = density . volume.
Density of propane is: 493 g/L
Mass of propane is 493 g/L . 27.9L = 13754.7 g
We convert mass to moles: 13754.7 g . 1 mol/ 44g = 312.6 moles
According to reaction, 1 mol of propane can produce 3 moles of CO₂
Our 312.6 moles will produce 312.6 . 3 = 937.8 moles
We convert moles to mass: 937.8 mol . 44 g/mol = 41264 g
Answer:
1.23 g/mL
-18.2%
Explanation:
We need to find the average, which is just the sum of the numbers divided by the number of numbers. Here, the sum will be 1.24 + 1.21 + 1.23 = 3.68 g/mL. There are 3 numbers, so divide 3.68 by 3: 3.68 / 3 ≈ 1.2266...
However, we need to round this and take into account significant figures. Each trial gave a number with 3 significant figures, so we round our number off to three: 1.22666... ≈ 1.23. So, circle the first number under the X column.
We now need to find the percent error, which is RE (%). To calculate this, we take the measured value (1.23 in this case) and subtract the exact value (1.50 here) from it, and then divide that by the exact value:
(1.23 - 1.50) / 1.50 ≈ -0.1822...
Again, we need to round to 3 significant figures, which would make it:
-0.1822... ≈ -0.182
Thus, circle the last number under the RE (%) column.
Answer:
Wave theory of light that states that visible light irrespective of its color, can cause the ejection of electrons when it strikes a metal.
Explanation:
Wave theory of light:
- If we go through wave theory of light, it clearly focuses that light is of actually wave nature not particle nature.
- The wave theory was based on the ideas of Hertz who discovered in 1887 that metallic surface can emit heat energy (electrons) when light hits the metal. If we increase the intensity of light, it will also increase the incident energy and ultimately increase the kinetic energy of electrons.
- Moreover, the frequency of light do not matters much, just a beam of light can eject the electrons from the metal.
Photoelectric effect:
On the other hand, Photoelectric effect can be considered only if we assume that light has particle like nature and not wave like nature.
- It also says that frequency of light matters alot in ejecting the electrons from the metals. If the frequency of light is less, it will not eject electrons from the metal surface even if it falls on metal for a very long time.
- It also says that maximum kinetic energy of the electrons (that are emitted) corresponds with the light frequency that caused the emission of electrons.
- The current of emitted electrons is directly proportional to the intensity of light that caused the electron emission.
We can see that the postulates of wave theory (like no.3) are just opposite to the postulates of photoelectric effect. The photoelectric effect also explained the relationship between emitted electrons and light in a better way that was not described by wave theory. We can say that it is as advanced explanation of facts based on the classical theory of wave like nature of visible light.
