<span>a) 7.9x10^9
b) 1.5x10^9
c) 3.9x10^4
To determine what percentage of an isotope remains after a given length of time, you can use the formula
p = 2^(-x)
where
p = percentage remaining
x = number of half lives expired.
The number of half lives expired is simply
x = t/h
where
x = number of half lives expired
t = time spent
h = length of half life.
So the overall formula becomes
p = 2^(-t/h)
And since we're starting with 1.1x10^10 atoms, we can simply multiply that by the percentage. So, the answers rounding to 2 significant figures are:
a) 1.1x10^10 * 2^(-5/10.5) = 1.1x10^10 * 0.718873349 = 7.9x10^9
b) 1.1x10^10 * 2^(-30/10.5) = 1.1x10^10 * 0.138011189 = 1.5x10^9
c) 1.1x10^10 * 2^(-190/10.5) = 1.1x10^10 * 3.57101x10^-6 = 3.9x10^4</span>
A flask with a volume of 125.0 mL contains air with a density of 1.298 g/L. what is the mass of the air contained in the flask<span>The given are: </span>
<span><span>1. </span>Mass = ?</span><span><span /></span>
<span><span>2. </span>Density = 1298 g/L</span>
3. Volume = 125mL to L
a. 125 ml x 0.001l/1ml = 0.125 L
<span>Formula and derivation: </span><span><span>
1. </span>density = mass / volume</span> <span><span>
2. mass </span>= density / volume</span>
<span>Solution for the problem: </span><span><span>
1. mass = </span></span> <span> 1298 g/L / 0.125 L = 10384g
</span>
Answer: 0.004 moles
Explanation:
Amount of substance= mass/ molar mass
Mass= 250mg or 0.25g
Molar mass= 58.44gmol-1
Amount= 0.25/58.44
= 0.004 moles
O.N. of Na = +1
O.N. of O = -2
Let, O.N. of Tin = x
1*2 + x + -2*2 = 0
2+x-4 = 0
x-2 = 0
x = 2
SO OPTION C IS YOUR ANSWER......
2.5X20=50g
50g should be the right answer
Mass=volumeXdenisty.
