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Iteru [2.4K]
4 years ago
6

Lt takes 4 hr 39 min for a 2.00-mg sample of radium-230 to decay to 0.25 mg. what is the half-life of radium-230?

Chemistry
1 answer:
Rufina [12.5K]4 years ago
6 0
Radioactive decay => C = Co { e ^ (- kt) |

Data:

Co = 2.00 mg
C = 0.25 mg
t = 4 hr 39 min

Time conversion: 4 hr 39 min = 4.65 hr

1) Replace the data in the equation to find k

C = Co { e ^ (-kt) } => C / Co = e ^ (-kt) => -kt = ln { C / Co} => kt = ln {Co / C}

=> k = ln {Co / C} / t =  ln {2.00mg / 0.25mg} / 4.65 hr = 0.44719

2) Use C / Co  = 1/2 to find the hallf-life

C / Co = e ^ (-kt) => -kt = ln (C / Co)

=> -kt = ln (1/2) => kt = ln(2) => t = ln (2) / k

t = ln(2) / 0.44719 = 1.55 hr.

Answer: 1.55 hr
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Viefleur [7K]

Answer:

P_2=404 kPa

Explanation:

Hello,

In this case, the Boyle's is mathematically defined via:

P_1V_1=P_2V_2

Which stands for an inversely proportional relationship between volume and pressure, it means the higher the volume the lower the pressure and vice versa. In such a way, since the volume is decreased to one quarter, we can write:

V_2=\frac{1}{4} V_1

We can compute the new pressure:

P_2=\frac{P_1V_1}{V_2} =\frac{P_1V_1}{\frac{1}{4} V_1} =\frac{101kPa*V_1}{\frac{1}{4} V_1} \\\\P_2=4*101kPa\\\\\\P_2=404 kPa

Which means the pressure is increased by a factor of four.

Regards.

7 0
3 years ago
If 38.5 grams of potassium react with excess oxygen gas, how many grams of potassium oxide can be produced? 4K + O2 yields 2K2O
Lera25 [3.4K]

Answer:

46.40 g.

Explanation:

  • It is a stichiometric problem.
  • The balanced equation of the reaction: 4K + O₂ → 2K₂O.
  • It is clear that 4.0 moles of K reacts with 1.0 mole of oxygen produces 2.0 moles of K₂O.
  • We should convert the mass of K (38.5 g) into moles using the relation:

<em>n = mass / molar mass,</em>

n = (38.5 g) / (39.098 g/mol) = 0.985 mole.

<em>Using cross multiplication:</em>

4.0 moles of K produces → 2.0 moles of K₂O, from the stichiometry.

0.985 mole of K produces → ??? moles of K₂O.

∴ The number of moles of K₂O produced = (0.985 mole) (2.0 mole) / (4.0 mole) = 0.4925 mole ≅ 0.5 mole.

  • Now, we can get the mass of K₂O:

∴ mass = n x molar mass = (0.5 mole) (94.2 g/mol) = 46.40 g.

6 0
3 years ago
how the various concentrations of acid will affect the amount of limestone that is dissolved from each jar.
schepotkina [342]

The explanation of the how the various concentrations of acid will affect the amount of limestone has been given below.

Effects of acid rain on limestone:-

  • When an acid combines with a carbonate, it produces carbon dioxide as a gas and forms a salt that is soluble in the carbonate and acid's water.
  • There are several gases in the atmosphere that can dissolve in precipitation such as rain and snow.
  • Some may produce acids in rain water, such as carbonic acid, sulfuric acid, and nitric acid.
  • Because the concentration is modest, the rain is not highly acidic, but it is acidic enough to react with the carbonates that make up limestone.

Thus we discussed the affects of acid rain on limestones above.

Learn more about Acid Rain here:

brainly.com/question/718250

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8 0
2 years ago
Balance it by oxidation number method:Zn +HNO3----Zn(NO3)2+NO+H2O​
timofeeve [1]

Answer:

Answer:

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Zn +HNO3➔Zn(NO3)2+NO+H2O

step 2: identity undergoing oxidation or reduction

here

Zn➔Zn(NO3)2

Zn is oxidized from 0 to 2 in oxidation no.

HNO3➔NO

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Step 3: calculate change in oxidation no.

change in oxidation no

in Zn=0-2=-2=2

in

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Step 4: Balance it by doing crisscrossed multiplication

we get;

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step 6:Balance other atoms except H & O

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3Zn +2HNO3+6HNO3➔3Zn(NO3)2+2NO+H2O

finally: balance H

<em><u>3Zn +8HNO3➔3Zn(NO3)2+2NO+4H2O</u></em>

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While metallic bonds have the strong electrostatic force of attractions between the cation or atoms and the delocalized electrons in the geometrical arrangement of the two metals. ... Metallic bonds are malleable and ductile, while covalent bonds and ionic bonds non-malleable and non-ductile.

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