0.139 moles of plutonium are present in a sample containing 8.4 x 10²² atoms of Pt.
<h3>How to calculate number of moles?</h3>
The number of moles of a substance can be calculated using the following expression:
no of moles = no of molecules ÷ 6.02 × 10²³
According to this question, 8.4 × 10²² atoms of plutonium are present in the molecule of plutonium.
no of moles = 8.4 × 10²² = 6.02 × 10²³
no of moles = 1.39 × 10-¹
no of moles = 0.139moles
Therefore, 0.139 moles of plutonium are present in a sample containing 8.4 x 10²² atoms of Pt.
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Answer : The time passed in days is 28.6 days.
Explanation :
Half-life = 14.3 days
First we have to calculate the rate constant, we use the formula :
![k=\frac{0.693}{t_{1/2}}](https://tex.z-dn.net/?f=k%3D%5Cfrac%7B0.693%7D%7Bt_%7B1%2F2%7D%7D)
![k=\frac{0.693}{14.3\text{ days}}](https://tex.z-dn.net/?f=k%3D%5Cfrac%7B0.693%7D%7B14.3%5Ctext%7B%20days%7D%7D)
![k=4.85\times 10^{-2}\text{ days}^{-1}](https://tex.z-dn.net/?f=k%3D4.85%5Ctimes%2010%5E%7B-2%7D%5Ctext%7B%20days%7D%5E%7B-1%7D)
Now we have to calculate the time passed.
Expression for rate law for first order kinetics is given by:
![t=\frac{2.303}{k}\log\frac{a}{a-x}](https://tex.z-dn.net/?f=t%3D%5Cfrac%7B2.303%7D%7Bk%7D%5Clog%5Cfrac%7Ba%7D%7Ba-x%7D)
where,
k = rate constant = ![4.85\times 10^{-2}\text{ days}^{-1}](https://tex.z-dn.net/?f=4.85%5Ctimes%2010%5E%7B-2%7D%5Ctext%7B%20days%7D%5E%7B-1%7D)
t = time passed by the sample = ?
a = let initial amount of the reactant = 100 g
a - x = amount left after decay process = 100 - 75.0 = 25.0 g
Now put all the given values in above equation, we get
![t=\frac{2.303}{4.85\times 10^{-2}}\log\frac{100}{25.0}](https://tex.z-dn.net/?f=t%3D%5Cfrac%7B2.303%7D%7B4.85%5Ctimes%2010%5E%7B-2%7D%7D%5Clog%5Cfrac%7B100%7D%7B25.0%7D)
![t=28.6\text{ days}](https://tex.z-dn.net/?f=t%3D28.6%5Ctext%7B%20days%7D)
Therefore, the time passed in days is 28.6 days.
Answer:
x = 1, -7.5
Explanation:
2x² + 13x = 15
Divide the left side of the equation by 2
2(x² + 6.5x) = 15
Divide 6.5 by 2 and square the quotient
6.5/2 = 3.25
3.25² = 10.5625
Add 10.5625 to the left side
2(x² + 6.5x + 10.5625) = 15
Since you have a 2 outside the parentheses, you will be adding 10.5625•2 to the right side.
10.5625 • 2 = 21.125
2(x² + 6.5x + 10.5625) = 36.125
To factor (x² + 6.5x + 10.5625), add b/2 to x
b/2 = 6.5/2 = 3.25
2(x + 3.25)² = 36.125
Divide by 2
(x + 3.25)² = 18.0625
Square root.
(x + 3.25) = √18.0625
x + 3.25 = ±4.25
Subtract 3.25.
x = 4.25 - 3.25 = 1
x = -4.25 - 3.25 = -7.5
x = 1, -7.5
Answer:
We know that 18 g of H2O contains 1 mole (or 6.022 x 10^23) molecules of water because the molar mass of H2O is 18 g/mol.
So 1 g water will contain 1/18 moles of H2O molecules.
Now 15 g of water will contain 15/18 moles of H2O.
So molecules of H2O = (15/18) x 6.022 x 10^23 = 5 x 10^23 molecules.
Explanation:
I learned this in science hope this helps.
Answer:
The answer would be at 120°C