The answer would be: element helium
Answer : The time taken for the concentration will be, 7.98 seconds
Explanation :
First order reaction : A reaction is said to be of first order if the rate is depend on the concentration of the reactants, that means the rate depends linearly on one reactant concentration.
Expression for rate law for first order kinetics is given by :
![k=\frac{2.303}{t}\log\frac{[A]_o}{[A]}](https://tex.z-dn.net/?f=k%3D%5Cfrac%7B2.303%7D%7Bt%7D%5Clog%5Cfrac%7B%5BA%5D_o%7D%7B%5BA%5D%7D)
where,
k = rate constant = 
t = time taken for the process = ?
= initial concentration = 0.860 M
= concentration after time 't' = 0.260 M
Now put all the given values in above equation, we get:


Therefore, the time taken for the concentration will be, 7.98 seconds
Refer to the diagram shown below.
Let T = the tension in each wire.
For equilibrium,
2T cos(50°) = 150 N
1.2856T = 150
T = 116.677 N ≈ 117 N
Answer: 117 N
-- Equations #2 and #6 are both the same equation,
and are both correct.
-- If you divide each side by 'wavelength', you get Equation #4,
which is also correct.
-- If you divide each side by 'frequency', you get Equation #3,
which is also correct.
With some work, you can rearrange this one and use it to calculate
frequency.
Summary:
-- Equations #2, #3, #4, and #6 are all correct statements,
and can be used to find frequency.
-- Equations #1 and #5 are incorrect statements.