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djyliett [7]
3 years ago
12

Uranium–232 has a half–life of 68.9 years. A sample from 206.7 years ago contains 1.40 g of uranium–232. How much uranium was or

iginally present?
Chemistry
2 answers:
Mnenie [13.5K]3 years ago
7 0

it's 11.2, other guy prob made a typo is all

givi [52]3 years ago
4 0

<u>Answer:</u> The initial amount of Uranium-232 present is 11.3 grams.

<u>Explanation:</u>

All the radioactive reactions follows first order kinetics.

The equation used to calculate half life for first order kinetics:

t_{1/2}=\frac{0.693}{k}

We are given:

t_{1/2}=68.9yrs

Putting values in above equation, we get:

k=\frac{0.693}{68.9}=0.0101yr^{-1}

Rate law expression for first order kinetics is given by the equation:

k=\frac{2.303}{t}\log\frac{[A_o]}{[A]}

where,

k = rate constant = 0.0101yr^{-1}

t = time taken for decay process = 206.7 yrs

[A_o] = initial amount of the reactant = ?

[A] = amount left after decay process = 1.40 g

Putting values in above equation, we get:

0.0101yr^{-1}=\frac{2.303}{206.7yrs}\log\frac{[A_o]}{1.40}

[A_o]=11.3g

Hence, the initial amount of Uranium-232 present is 11.3 grams.

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sorry if I am wrong I am dumb. :( :(

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. Calculate the molality of each of the following solutions: (a) 0.710 kg of sodium carbonate (washing soda), Na2CO3, in 10.0 kg
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Answer:

a)0.67 molal

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Explanation:

Step 1: Data given

Molality = moles solute / mass solvent

(a) 0.710 kg of sodium carbonate (washing soda), Na2CO3, in 10.0 kg of water—a saturated solution at 0°C

Calculate moles of Na2CO3 =  710 grams / 105.99 g/mol = 6.70 moles

Molality = 6.70 moles / 10 kg = 0.67 molal

(b) 125 g of NH4NO3 in 275 g of water—a mixture used to make an instant ice pack

Calculate moles of NH4NO3 = 125 grams / 80.04 g/mol = 1.56 moles

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0.372 g of histamine, C5H9N, in 125 g of chloroform, CHCl3

Calculate moles histamine = 0.372 grams / 111.15 g/moles = 0.00335 moles

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3 years ago
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Calcium nitrate is quite soluble in water due to very low lattice enthalpy in comparison to other ionic compound. With lower lattice enthalpy, less energy is required for the dissociation of calcium nitrate and it get dissolves in water than other three compounds. Moreover, hydration energy is higher for calcium nitrate which make its solubility higher in water than other ionic species.

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3 years ago
Which element in each of the following sets would you expect to have the lowest IE₃?
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Answer:

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(c)Al

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The higher the electron is on energy level the farther its from nucleus and more loosely bonded thus need lesser energy.

By looking at electron configuration we can figure out which electron will need more energy.

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Na₁₁ ⇒ 1s², 2s², 2p⁶, 3s¹

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Sc will have lowest IE₃ as its third electron will be in highest energy level and more loosely bonded to nucleus.

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Li₃ ⇒ 1s², 2s¹

Al₁₃ ⇒ 1s², 2s², 2p⁶, 3s², 2p¹

B₅ ⇒ 1s², 2s², 2p¹

Al will have lowest IE₃ as its third electron will be in highest energy level and more loosely bonded to nucleus.

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