Equation for Half life :
A = a(0.5)^(t/h)
A is current amount, "a" is initial amount, h is halflife, t is time
5 = 40(0.5)^(t/1.3x10^9)
5/40 = (0.5)^(t/1.3x10^9)
take the log of both sides , power rule
Log(5/40) = (t/1.3x10^9) * Log(0.5)
(1.3x10^9) * Log(5/40) / Log(0.5) = t
3.9x10^9 years = t
And if you think about what a half life is, the time it take for the amount to reduce to half.
40/2 = 20
20/2 = 10
10/2 = 5
It went through 3 half-lifes
3 * 1.3x10^9 = 3.9x10^9 years
Answer:
When combined with Hubble's visible-light data, astronomers can ... Dark things absorb light, but this invisible stuff neither absorbs, nor ... Is dark matter made of still undiscovered tiny particles, as most physicists suppose?
Explanation:
When paper burns, it releases two distinct forms of energy
Thermal Energy
Light Energy
Thermal Energy is heat energy, heat energy is formed from the flame on the paper, in this scenario.
Light energy comes from the reaction of the paper, the flame.
In conclusion, both energy's form from the reaction of the paper, and the combustion in the air. Thus, heat and light.
Answer:
Here's what I get
Explanation:
3. Molar concentration by formula.
(i) Comparison of molar concentrations
The formula gives a calculated value of 0.5302 mol·L⁻¹.
Dimensional analysis gives a calculated value of 0.1767 mol·L⁻¹.
The first value is three times the second.
It is wrong because the formula assumes that the acid supplies just enough moles of H⁺ to neutralize the OH⁻ from the NaOH.
Instead, I mol of H₃PO₄ provides 3 mol of H⁺, so your calculated concentration is three times the true value.
(ii) When is the formula acceptable?
The formula is acceptable only when the molar ratio of acid to base is 1:1.
Examples are
HCl + NaOH ⟶ NaCl + H₂O
H₂SO₄ + Ca(OH)₂ ⟶ CaSO₄ + 2H₂O
H₃PO₄ + Al(OH)₃ ⟶ AlPO₄ + 3H₂O