1 half-life - 4.5 days
x half-lives - 27 days
x=(1*27)/4.5=6
6 <span>half-lives have elapsed after 27 days.</span>
Answer: 3) 39.96 amu
Explanation:
Mass of isotope Ar- 36 = 35.97 amu
% abundance of isotope Ar- 36= 0.337% = 
Mass of isotope Ar- 38 = 37.96 amu
% abundance of isotope 2 = 0.063 % = 
Mass of isotope Ar- 40 = 39.96 amu
% abundance of isotope 2 = 99.600 % = 
Formula used for average atomic mass of an element :

![A=\sum[(35.97\times 3.37\times 10^{-3})+(37.96\times 6.3\times 10^{-4})+(39.96\times 0.996)]](https://tex.z-dn.net/?f=A%3D%5Csum%5B%2835.97%5Ctimes%203.37%5Ctimes%2010%5E%7B-3%7D%29%2B%2837.96%5Ctimes%206.3%5Ctimes%2010%5E%7B-4%7D%29%2B%2839.96%5Ctimes%200.996%29%5D)

Therefore, the average atomic mass of argon is 39.96 amu
Answer:
0.15g
Explanation:
Given parameters:
Number of molecules of water = 1.2 x 10²¹ molecules
Unknown:
Mass of SnO₂ = ?
Solution:
To solve this problem, we have to work from the known to the unknown specie;
SnO₂ + 2H₂ → Sn + 2H₂O
Ensure that the equation given is balanced;
Now,
the known species is water;
6.02 x 10²³ molecules of water = 1 mole
1.2 x 10²¹ molecules of water =
= 0.2 x 10⁻²moles
Number of moles of water = 0.002moles
From the balanced chemical equation:
2 mole of water is produced from 1 mole of SnO₂
0.002 moles of water will be produced from
= 0.001moles
To find the mass;
Mass = number of moles x molar mass
Molar mass of SnO₂ = 118.7 + 2(16) = 150.7g/mol
Mass = 0.001 x 150.7 = 0.15g
Answer:
0.209M
Explanation:
M1V1=M2V2
(28.5 mL)(0.183M)=(25.0mL)(M)
M2= 0.209M
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