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Alex
4 years ago
12

PLEASE ANSWER I NEED THE ANSWER ASAP!!!!!!!!!The table shows the amount of radioactive element remaining in a sample over a peri

od of time. Part 1: what is the half life of the element? Explain how you determined this.Part 2: how long would it take 308 g of the sample to decay to 4.8125 grams? Show your work or explain your answer? * please explain the answer is easy to understand terms, thank you*
Chemistry
1 answer:
qaws [65]4 years ago
3 0

Answer:

pt1

The half-life of the element is 1,600 years.

pt2

k = ln(2)/(t1/2) = 0.693/(t1/2).

Where, k is the rate constant of the reaction.

t1/2 is the half-life of the reaction.

∴ k =0.693/(t1/2) = 0.693/(1,600 years) = 4.33 x 10⁻⁴ year⁻¹.

kt = ln([A₀]/[A]),

where, k is the rate constant of the reaction (k = 4.33 x 10⁻⁴ year⁻¹).

t is the time of the reaction (t = ??? year).

[A₀] is the initial concentration of the sample ([A₀] = 312.0 g).

[A] is the remaining concentration of the sample ([A] = 9.75 g).

∴ t = (1/k) ln([A₀]/[A]) = (1/4.33 x 10⁻⁴ year⁻¹) ln(312.0 g/9.75 g) = [8,000 year].

-Hops

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A Cu2+ solution is prepared by dissolving a 0.4749 g piece of copper wire in acid. The solution is then passed through a Walden
Luda [366]

Answer:

Concentration of Cr_2O_7^{2-} = 0.03101 M

Concentration of MnO_4^- = 0.03721 M

Explanation:

A)

The reduction for Cr_2O_7^{2-} is;

Cr_2O_7^{2-} + 14 H ^+ _{(aq)}  + 6 e^- -----> 2 Cr^{3+} _{(aq)}+7H_2O _{(l)}

Cu^+_{(aq)} -----> Cu^{2+} _{(aq)} + 1 e^-

6 moles of Cu ^+ = 1 mole of Cr_2O_7^{2-}

number of moles of Cu reacted = \frac{mass \ of \ Cu \ wire }{ molecular weigh tof \ Cu wire }

number of moles of Cu reacted = \frac{0.4749}{63.55}

number of moles of Cu reacted = 0.00747 mole

number of moles of Cr_2O_7^{2-}reacted = \frac{0.00747}{6}

number of moles of Cr_2O_7^{2-}reacted = 0.001245 mole

Concentration of Cr_2O_7^{2-} = \frac{number \ of moles }{Volume}

Given that the volume = 40.15 mL = 40.15 *10^{-3}; we have:

Concentration of Cr_2O_7^{2-} = \frac{0.001245}{40.15*10^{-3}}

Concentration of Cr_2O_7^{2-} = 0.03101 M

B)

The reduction for MnO_4^- is;

MnO_4^- + 8H^+ + 5 e^- -----> Mn^{2+} + 4H_2O

Cu^+_{(aq)} -----> Cu^{2+} _{(aq)} + 1 e^-

5 moles of Cu ^+ = 1 mole of Cr_2O_7^{2-}

number of moles of Cu reacted = \frac{mass \ of \ Cu \ wire }{ molecular weigh tof \ Cu wire }

number of moles of Cu reacted = \frac{0.4749}{63.55}

number of moles of Cu reacted = 0.00747 mole

number of moles of MnO_4^- reacted = \frac{0.00747}{5}

number of moles of MnO_4^- reacted = 0.001494 mole

Concentration of MnO_4^- = \frac{number \ of moles }{Volume}

Given that the volume = 40.15 mL = 40.15 *10^{-3}; we have:

Concentration of MnO_4^- = \frac{0.001494 }{40.15*10^{-3}}

Concentration of MnO_4^- = 0.03721 M

3 0
4 years ago
How much energy, in joules, does 150.0 g of water with an initial temperature of 25 C need to absorb be raised to a final temper
satela [25.4K]

Answer:

31395 J

Explanation:

Given data:

mass of water = 150 g

Initial temperature = 25 °C

Final temperature = 75 °C

Energy absorbed = ?

Solution:

Formula:

q = m . c . ΔT

we know that specific heat of water is 4.186 J/g.°C

ΔT = final temperature - initial temperature

ΔT = 75 °C - 25 °C

ΔT = 50 °C

now we will put the values in formula

q = m . c . ΔT

q = 150 g × 4.186 J/g.°C × 50 °C

q = 31395 J

so, 150 g of water need to absorb 31395 J of energy to raise the temperature from 25°C to 75 °C .

5 0
3 years ago
What is the molar mass of 12?
andrew-mc [135]

Answer:

I assume your talking about carbon when you say 12 so it'd be 12 grams if you are

Explanation:

The molar mass of any substance in grams per mole is numerically equal to the mass of that substance expressed in atomic mass units.

Hope this helps you some

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ki77a [65]
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