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2 years ago

How many days does it take 16.Og of Gold-198 to decay to 1.0g? (each half-

Chemistry

1 answer:

forsale [732]2 years ago

4 0

Answer:

10.8 days (3 sig.figs.)

Explanation:

All radioactive decay is 1st order decay defined by the expression A = A₀e^-kt

which is solved for time of decay (t) => t = ln(A/A₀) / -k

A = final weight = 1.0 gram

A₀ = initial weight = 16.0 grams

k = rate constant = 0.693/t(1/2) = 0.693/2.69 days = 0.258 days⁻¹

t = ln(1/16) / -0.258da⁻¹ = (-2.77/-0.258) days = 10.74646792 days (calculator)

≅ 10 days (1 sig. fig. based on given 1 gram mass)

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A student did not read the direction to the experiment properly and mixed up where to place the NaOH solution and the vinegar. H

Mariana [72]

Answer:

At end point there will a transition from pink to colorless.

Explanation:

As the student put the vinegar in the titrator and NaOH in the beaker, it means that he has poured phenolphthalein in the NaOH solution.

The pH range of phenolphthalein is 8.3-10 (approx), it means it will show pink color in basic medium.

So on addition of phenolphthalein in NaOH the solution will become pink in color.

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On complete neutralization , on addition of single drop of vinegar the solution will become acidic and there will be complete disappearance of pink color solution in the beaker.

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3 years ago

How many moles of H2SO4 are needed to completely neutralize 0.0164 mol KOH

Vanyuwa [196]

0.0082 You have to equal out the amount of concentration with the unknown

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3 years ago

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10) Air masses are different in many ways. Which of these is NOT different?

grandymaker [24]

Answer:D. Ratio of oxygen/nitrogen

Explanation: the ratio will never change no matter the air pressure!

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2 years ago

Help me, I’m failing chem

ladessa [460]

Answer:

Explanation:

[H3O+] = 10-pH = 10-3.4 ≅ 3.981 x 10^-4 moles/liter

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3 years ago

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Calculate the molality of a solution that contains 51.2 g of naphthalene, C10H8, in 500 mL of carbon tetrachloride. The density

PtichkaEL [24]

<u>Answer:</u> The molality of naphthalene solution is 0.499 m

<u>Explanation:</u>

Density is defined as the ratio of mass and volume of a substance.

$\text{Density}=\frac{\text{Mass}}{\text{Volume}}$ ......(1)

Given values:

Volume of carbon tetrachloride = 500 mL

Density of carbon tetrachloride = 1.60 g/mL

Putting values in equation 1, we get:

$\text{Mass of carbon tetrachloride}=(1.60g/mL\times 500mL)=800g$

Molality is defined as the amount of solute expressed in the number of moles present per kilogram of solvent. The units of molarity are mol/kg. The formula used to calculate molarity:

$\text{Molality of solution}=\frac{\text{Given mass of solute}\times 1000}{\text{Molar mass of solute}\times \text{Mass of solvent (in g)}}$ .....(2)

Given values:

Given mass of naphthalene = 51.2 g

Molar mass of naphthalene = 128.17 g/mol

Mass of solvent = 800 g

Putting values in equation 2, we get:

$\text{Molality of naphthalene}=\frac{51.2\times 1000}{128.17\times 800}\\\\\text{Molality of naphthalene}=0.499m$

Hence, the molality of naphthalene solution is 0.499 m

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2 years ago