Answer:
Explanation:
Given that,
The wavelength of a microwave is 7.42 mm or 0.00742 m
No. of photons, n = 359
We need to find the energy produced by this no of photons. It can be given by the formula as follows :
or
So, the required energy is 
.
Oxygen and selenium both have 6 valence electrons. They're in the same group hope this helps
B) 50 J because it had less energy at the beginning than the end
Answer:
Mole Fraction = 0.059
Explanation:
To find the mole fraction, you need to (1) convert grams H₂SO₄ and H₂O to moles (via molar mass) and then (2) calculate the mole fraction.
(Step 1)
Molar Mass (H₂SO₄): 98 g/mol
34 grams H₂SO₄ 1 mole
-------------------------- x ------------------- = 0.347 moles H₂SO₄
98 grams
Molar Mass (H₂O): 18 g/mol
100 grams H₂O 1 mole
------------------------- x -------------------- = 5.56 moles H₂O
18 grams
(Step 2)
moles solute
Mole Fraction = -------------------------------------------------
moles solute + moles solvent
0.347 moles H₂SO₄
Mole Fraction = -----------------------------------------------------------
0.347 moles H₂SO₄ + 5.56 moles H₂O
Mole Fraction = 0.059
The sample of cobalt-60 (t₁/₂= 5.27 yr) must be replaced after 2.7 years which makes 2 years and 8.4 months. if the sample was purchased on march 2012 then it must be replaces on mid January 2015.
<h3>Briefly explained</h3>
To determine when the cobalt 60 needs to be replaced when it has achieved 70% of the activity. We simply need to use the first order integrated rate law which will allow us to calculate the time. However, when using this equation we need the Decay constant for Cobalt 60, which we can get from the half life of Cobalt 60.
We simply divide the half life of 5.27 years into the natural log of two and we get .13151 over years. If we have reached 70 Then 70% expressed as a decimal .7. So we have .7 of an original amount of one. So you can think of this as being divided by one. So the natural log of the amount at time T divided by the original amount is equal to negative K. Which we just calculated, multiplied by T.
With some algebraic rearrangement we get 2.7 years. So 2.7 years from the purchase of March one in 2012 is approximately early 2015.
Learn more about decay
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