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djyliett [7]
2 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]2 years ago
7 0

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

givi [52]2 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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Convert 2.1 mole of Al2(SO4)3 ionic units to a number of particles.​
Semenov [28]

1.26 x 10²⁴particles

Explanation:

Given parameters:

Number of moles of the compound = 2.1 moles

Unknown:

Number of particles contained in the compound = ?

Solution:

A mole can be defined as the amount of a substance that contains Avogadro's number of particles 6.02 x 10²³.

The particles mentioned here can be atoms, molecules, formula units, ions, electrons, protons, neutrons and so forth.

To solve for the number of moles:

   Number of particles  = number of moles x 6.02 x 10²³

Number of particles = 2.1 x  6.02 x 10²³ = 12.64 x  10²³ = 1.26 x 10²⁴particles

Learn more:

mole calculation brainly.com/question/1841136

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8 0
2 years ago
A 12.2-g sample of x reacts with a sample of y to form 78.9 g of xy. what is the mass of y that reacted?
Sonja [21]
We will assume that the only reactants are x and y and that the only product is xy.

Based on the law of mass conservation, mass is an isolated system that can neither be created nor destroyed.

Applying this concept to the chemical reaction, we will find that the total mass of the reactants must be equal to the total mass of the products,
therefore:
mass of x + mass of y = mass of xy
12.2 + mass of y = 78.9
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4 0
2 years ago
Calculate the molar mass of a gas that diffuses three times faster than oxygen under similar conditions.
JulsSmile [24]
<span> rate 3/1= square root of 32/x
square both sides
9/1=32x
x = 32/9
= 3.6
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</span>
7 0
2 years ago
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The volume of a single strontium atom is 4.15×10-23 cm3. What is the volume of a strontium atom in microliters
Ivenika [448]

Answer:-  4.15*10^-^2^0\mu L

Solution:- It is a volume unit conversion problem where we are asked to convert the volume from cm^3 to microliters.

We know that:

1cm^3 = 1 mL

1mL=10^-^3L

and, 1L=10^6\mu L

Let's use these conversions factors for the desired conversion using dimensional as:

4.15*10^-^2^3cm^3(\frac{1mL}{1cm^3})(\frac{10^-^3L}{1mL})(\frac{10^6\mu L}{1L})

= 4.15*10^-^2^0\mu L

So, the answer is  4.15*10^-^2^0\mu L .

7 0
2 years ago
There are ________ hydrogen atoms in 25 molecules of c4h4s2.
coldgirl [10]

Answer: 100.


Explanation:


1) The subscripts to the right of each element (symbol) in the chemical formula tells the number of atoms of that element present in one unit formula.


2) The unit formula of C₄H₄S₂ is equal to 1 molecule.


3) Therefore, there are 4 carbon atoms, 4 hydrogen atoms and 2 sulfur atoms in each molecule of C₄H₄S₂.


4) Then, you just have to multiply the corresponding subscript of the element times the number of molecules (25 in this case) to find the number of atoms of that kind.


5) These are the calculations for each element in the molecule C₄H₄S₂.


i) C: 4 × 25 = 100

ii) H: 4 × 25 = 100

iii) S: 2 × 25 = 50.


6) The question is about H only, so the answer is that there are 100 hydrogen atoms in 25 molecules of C₄H₄S₂.

5 0
2 years ago
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