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3 years ago

What is the molarity of a solution in which 25g NaCl in a 2.00 L solution?

Chemistry

1 answer:

Paladinen [302]3 years ago

5 0

Mass of sodium :- 23 grams

Mass of Chlorine :- 35.5 grams

Mass of NaCl :- 58.5 grams

mass given :- 25 grams

moles :- 0.432 ( given mass/ ionic mass)

$molarity = \frac{moles}{vol} \\ molarity = \frac{0.432}{2} \\ molarity = 0.216 \: mole{l}^{ - 1} or \: molar$

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One of the main contaminants of a nuclear accident, such as that at Chernobyl, is strontium-90, which decays exponentially at an

igor_vitrenko [27]

Answer: a) %(C/Co) = (e^(-0.027t)) × 100

b) t1/2 = 25.67years

c) 5.872%

Explanation:

a) Radioactive reactions always follow a first order reaction dynamic

Let the initial concentration of Strontium-90 be Co and the concentration at any time be C

The rate of decay will be given as:

(dC/dt) = -KC (Minus sign because it's a rate of reduction)

The question provides K = 2.7% per year = 0.027/year

(dC/dt) = -0.027C

(dC/C) = -0.027dt

∫ (dC/C) = -0.027 ∫ dt

Solving the two sides as definite integrals by integrating the left hand side from Co to C and the Right hand side from 0 to t.

We obtain

In (C/Co) = -0.027t

(C/Co) = (e^(-0.027t))

In percentage, %(C/Co) = (e^(-0.027t)) × 100

(Solved)

b) Half life of a first order reaction (t1/2) = (In 2)/K

K = 0.027/year

t1/2 = (In 2)/0.027 = 25.67 years

c) percentage that remains after 105years,

%(C/Co) = (e^(-0.027t)) × 100

t = 105

%(C/Co) = (e^(-0.027 × 105)) × 100 = 5.87%

8 0

3 years ago

We have a 1 liter sample of water containing 1.4 mg lead per mL. Lead levels in water above 0.25 ug/mL are unsafe to drink. We c

Orlov [11]

Answer:

79 extractions

Explanation:

An isooctane/water partinioning constant of 12/1 means that 12 out of 13 parts of the Pb²⁺ complex will be found in isooctane, while the remaining 1 out of 13 part will remain in water.

12/13 * 100 = 92.3% of the Pb²⁺ will be removed with each extraction.

Now we convert 1.4 mg/mL to ug/mL:

1.4 $\frac{mg}{mL} * \frac{100ug}{1mg}$ = 140 ug/mL

We're looking to have a final concentration of 0.25 ug/mL, so we can write:

140 mg/mL * (0.923)ⁿ = 0.25 ug/mL

Where n is the number of extractions.

We solve for n:

(0.923)ⁿ = 1.786x10⁻³

n = ln (1.786x10⁻³) / ln (0.923)

n = 79

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3 years ago

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Hitman42 [59]

False is the answer

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3 years ago

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Andreas93 [3]

Answer:

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3 years ago

Describe the difference between intensive and extensive propoerties. Which of the following propoerties are intensive: (a) mass;

STatiana [176]

Answer:

The properties that do not vary with the variation in the quantity of the material are called as intensive property.

While the extensive properties are those which vary with the variation in the quantity of the material.

Intensive properties:

Mass and volume

Extensive properties:

Density and melting point

Explanation:

The properties that do not vary with the variation in the quantity of the material are called as intensive property.

While the extensive properties are those which vary with the variation in the quantity of the material.

Intensive properties:

Mass and volume, as with increase in quantity of the material mass and volume increases.

Extensive properties:

Density and melting point, as they remain constant for a object or material

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4 years ago