What element is used to make expensive forks spoons and tableware?

After 11.5 days, 12.5% of a sample of radon-222 that originally weighed 42g remains. What is the half-life of this isotope?

Bond [772]

Half-life is defined as the amount of time it takes a given quantity to decrease to half of its initial value. The equation to describe the decay is
Nt=N0(1/2) $^{t/t(1/2)}$ where N0 is the initial quantity, Nt is the remaining quantity after time t, t1/2 is the half-time. So work out the equation, t1/2 = t (-ln2)/ln(Nt/N0) = 11.5*(-ln2)/ln(12.5/100) = 3.83 days

5 0

3 years ago

Using the thermodynamic information in the ALEKS Data tab, calculate the standard reaction entropy of the following chemical rea

Aleksandr [31]

Answer:

ΔS° = - 47.2 J/mol.K

Explanation:

P4O10 + 6H2O → 4H3PO4

ΔS°= 4(S°mH3PO4) - 6(S°mH2O) - S°mP4O10

∴ S°mH2O(l) = 69.9 J/mol.K

∴ S°mP4O10 = 231 J/mol.K

∴ S°mH3PO4 = 150.8 J/mol.K

⇒ ΔS° = 4*(150.8) - 6*(69.9) - 231

⇒ ΔS° = - 47.2 J/mol.K

5 0

2 years ago

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If you mix 50mL of 0.1 M TRIS acid with 60 mL of0.2 M TRIS base, what will be the resulting pH?

Katyanochek1 [597]

Answer: The pH of resulting solution is 8.7

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in mL)}}$

For TRIS acid:

Molarity of TRIS acid solution = 0.1 M

Volume of solution = 50 mL

Putting values in above equation, we get:

$0.1M=\frac{\text{Moles of TRIS acid}\times 1000}{50mL}\\\\\text{Moles of TRIS acid}=0.005mol$

For TRIS base:

Molarity of TRIS base solution = 0.2 M

Volume of solution = 60 mL

Putting values in above equation, we get:

$0.2M=\frac{\text{Moles of TRIS base}\times 1000}{60mL}\\\\\text{Moles of TRIS base}=0.012mol$

Volume of solution = 50 + 60 = 110 mL = 0.11 L (Conversion factor: 1 L = 1000 mL)

To calculate the pH of acidic buffer, we use the equation given by Henderson Hasselbalch:

$pH=pK_a+\log(\frac{[salt]}{[acid]})$

$pH=pK_a+\log(\frac{[\text{TRIS base}]}{[\text{TRIS acid}]})$

We are given:

$pK_a$ = negative logarithm of acid dissociation constant of TRIS acid = 8.3

$[\text{TRIS acid}]=\frac{0.005}{0.11}$

$[\text{TRIS base}]=\frac{0.012}{0.11}$

pH = ?

Putting values in above equation, we get:

$pH=8.3+\log(\frac{0.012/0.11}{0.005/0.11})\\\\pH=8.7$

Hence, the pH of resulting solution is 8.7

6 0

3 years ago

Approximately how many particles are in 2 moles?

schepotkina [342]

Answer:

$1.2\times10^2^4$ particles in 2 moles.

Explanation:

The number of particles that are contained in one mole, the international unit of amount of substance: by definition, exactly 6.022×10²³, and it is dimensionless. It is named after the scientist Amedeo Avogadro.

It is also known as Avogadro's constant.

∴ Number of particles in one mole = $6.022\times10^2^3$

∴ Number of particles in 2 mole = 2 times Number of particles in one mole

∴ Number of particles in 2 mole= $2\times6.022\times10^2^3=12.044\times10^2^3\approx1.2\times10^2^4$

Hence there are $1.2\times10^2^4$ particles in 2 moles.

4 0

2 years ago

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A _____________ is formed when water empties into a lake or ocean

solong [7]

Answer:

a delta

Explanation:

he place where a river enters a lake, larger river, or the ocean is called its mouth. River mouths are places of much activity. As a river flows, it picks up sediment from the river bed, eroding banks, and debris on the water. ... When large amounts of alluvium are deposited at the mouth of a river, a delta is formed.

6 0

2 years ago