Answer:
1st step : find the number of moles for the known substance
number of moles =mass/ relative molecular mass
n=23/Li2O2
n=23/(14+32)
n =23/46
n= 0,5moles
2nd step : balance the equation
2Li202 +2H20-----> 4LiOH +O2
3rd step : find the mole ratio of the known or stated using the balanced equation
Li2O2 : O2
2 : 1
4th step :find the number of moles for the asked using the mole ratio using simple proportion
Li2O2 :O2
2 :1
0,5 :???
0,5/2 ×1
= 0,25moles for (O2)
5th step : find the asked either mass , volume , concentration
number of moles = volume/molar gas volume
volume = number of moles × molar gas volume
v = 0,25moles × 28dm^3
v= 7 dm^3 of (O2)
The answer is obviously d
A superconductor performs best at very cold temperatures.
<h3>
Answer:</h3>
28.52 seconds
<h3>
Explanation:</h3>
Initial number of atoms of Nitrogen 12,000 atoms
Half-life = 7.13
Number of atoms after decay = 750 atoms
We are required to determine the time taken for the decay.
Note that half life is the time taken for a radioactive isotope to decay to a half of its original amount.
Using the formula;
Remaining amount = Initial amount × (1/2)^n , where n is the number of half lives
In our case;
750 atoms = 12,000 atoms × (1/2)^n
0.0625 = 0.5^n
n = log 0.0625 ÷ log 0.5
n = 4
But, 1 half life =7.13 seconds
Therefore;
Time taken = 7.13 seconds × 4
= 28.52 seconds
Therefore, the time taken for 12,000 atoms of nitrogen to decay to 750 atoms is 28.52 seconds
