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 : The rms speed of the molecules in a sample of 
gas at 300 K will be four times larger than the rms speed of 
molecules at the same temperature, and the ratio 
constant with increasing temperature.
Explanation :
Formula used for root mean square speed :
where,
= rms speed of the molecule
R = gas constant
T = temperature
M = molar mass of the gas
At constant temperature, the formula becomes,
And the formula for two gases will be,
Molar mass of = 32 g/mole
Molar mass of = 2 g/mole
Now put all the given values in the above formula, we get
Therefore, the rms speed of the molecules in a sample of gas at 300 K will be four times larger than the rms speed of molecules at the same temperature.
And the ratio constant with increasing temperature because rms speed depends only on the molar mass of the gases at same temperature.
Answer:
1,260 is your answer plz mark if this right
Explanation:
In photograph a, a coil of zinc metal is in a solution of sulfuric acid. In photograph b, a yellow solution of sodium chromate is being added to a colorless solution of silver nitrate. What clues in the photographs indicate that a chemical change is probably occurring.
In photograph a, chemical change is occuring as when a coil of zinc metal is in a solution of sulfuric acid, then the solution starts bubbling, that indicates a chemical change.
In photograph b, a yellow solution of sodium chromate is being added to a colorless solution of silver nitrate, that changes the color of the solution to red , that indicates a chemical change.
