22. Sodium-24 has a half-life of 15 hours. How much sodium-24 will remain in an 42.0-g sample after 90 hours?
1 answer:
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Answer:
2Li + F₂ → 2LiF
Explanation:
The reaction expression is given as:
Li + F₂ → LiF
We are to balance the expression. In that case, the number of atoms on both sides of the expression must be the same.
Let use a mathematical approach to solve this problem;
Assign variables a,b and c as the coefficients that will balance the expression:
aLi + bF₂ → cLiF
Conserving Li: a = c
F: 2b = c
let a = 1, c = 1 and b =
Multiply through by 2;
a = 2, b = 1 and c = 2
2Li + F₂ → 2LiF
[H_{3}O^{+}] = 0.00770 M
The equilibrium equation representing the dissociation of
Given [H_{3}O^{+}] = 0.00770 M
Let the initial concentration of acid be x and change y
So y = =
= 0.00770 M
0.00257 x - 0.00001979 = 0.00005929
x = 0.031 M
Therefore, initial concentration of the weak acid is <u>0.031 M</u>