Lighting a match changes chemical energy into heat.
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Answer:
31.3grams
Explanation:
The amount of a radioactive element that remains, N(t), can be calculated by using the formula;
N(t) = N(o) × 0.5^{t/t(1/2)}
Where;
N(t) = mass of substance remaining
N(o) = mass of original substance
t(1/2) = half-life of substance
t = time elapsed
From the provided information; N(t) = ?, N(o) = 250g, t(1/2) = 1599 years, t = 4797 years
N(t) = 250 × 0.5^{4797/1599}
N(t) = 250 × 0.5^(3)
N(t) = 250 × 0.125
N(t) = 31.25g
N(t) = 31.3grams
Answer:
Wt Avg Atomic Wt = 28.0577 amu
Explanation:
Atomic Mass = ∑Wt Avg contributions of isotopes of an element
Si-28 => 92.21% => 0.9221 decimal fraction => Wt Avg Si-28 = 0.9221(27.9769) = 25.7695 amu
Si-29 => 4.69% => 0.0469 decimal fraction => Wt Avg Si-29 = 0.0469(28.9765) = 1.3590 amu
Si-30 => 3.10% => 0.0310 decimal fraction => Wt Avg Si-30 = 0.0310(29.9737) = 0.9292
Wt Avg Atomic Wt = ∑Wt Avg Contributions = (25.7695 + 1.3590 + 0.9292)amu = 28.0577 amu