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m_a_m_a [10]
3 years ago
9

The half-life of radium-226 is 1590 years. (a) A sample of radium-226 has a mass of 50 mg. Find a formula for the mass of the sa

mple that remains after t years. (b) Find the mass after 500 years correct to the nearest milligram. (c) When will the mass be reduced to 40 mg
Chemistry
1 answer:
Maksim231197 [3]3 years ago
4 0

Answer:

Explanation:

a )

m = m₀ e^{-\lambda t

m is mass after time t . original mass is m₀ , λ is disintegration constant

λ = .693 / half life

= .693 / 1590

= .0004358

m = m₀ e^{- 0.0004358 t}

b )

m = 50 x e^{-.0004358\times 500}

= 40.21 mg .

c )

40 = 50 e^{-.0004358t

.8 = e^{-.0004358t

e^{.0004358t = 1.25

.0004358 t = .22314

t = 512 years .

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Answer:

a. H₂O (conjugate acid) ; b. OH⁻ (conjugate base), H₃O⁺ (conjugate acid) ; c. H₂CO₃ (conjugate acid), CO₃⁻² (conjugate base) ; d. NH₄⁺ (conjugate strong acid) e. H₂SO₄ (conjugate acid), SO₄⁻² (conjugate base) ; f. No conjugate acid either base;  g. H₂S (conjugate acid), S⁻² (conjugate base);

h. H₄N₂ (conjugate base)

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The hydroxide acts like a Bronsted Lory base, so it can catch a proton. Water will be the conjugate acid.

b. H₂O, is an amphoterus compound. It can act as an acid or a base. If it is a base, the conjugate acid is the H₃O⁺. If it is an acid, the conjugate base is the OH⁻.

c. HCO₃⁻  +  H⁺  ⇄  H₂CO₃

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The bicarbonate is also amphoteric. When it catches the proton, the carbonic acid is the conjugate acid, cause it works as a base.

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e. Another amphoteric compound. The acid sulfate acts an acid and a base.

(like bicarbonate). When it is a base, the conjugate acid is the sulfuric acid, when it is an acid, the conjugate base is the sulfate.

HSO₄⁻  +  H₂O  ⇄  SO₄⁻²  +  H₃O⁺

HSO₄⁻  +  H⁺  ⇄  H₂SO₄

f. H₂O₂ does not recieve H⁺ or OH⁻, and it does not release H⁺. It is a neutral compound and it doesn't act as a base or acid.

g. HS⁻ is amphoterous.

HS⁻  +  H⁺  ⇄  H₂S

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