All categories

3 years ago

What would the percentage of thorium-232 (parent compound) be in a rock that was dated at 2.8 billions years?

Chemistry

1 answer:

just olya [345]3 years ago

5 0

The half-life of Th-232 is 1.405 × 10¹⁰ years

Time elapsed = 2.8 x 10⁹ years

Equation of radioactive decay:

A = A₀ = (1/2)^ t/t₁/₂

where A₀ is the initial amount, A is the amount after time t, t₁/₂ is the half file

The fraction of thorium-232 that remains in the rock after 2.8 billions years is,

A/A₀ = (1/2) ^ (2.8 x 10⁹/ 1.405 × 10¹⁰) = 0.871

Therefore, the percentage of thorium-232 in the rock that was dated at 2.8 billions year = 87.1%

You might be interested in

NEED HELP FAST I WILL MARK BRAINLIEST AND THANK YOU AND RATE 5 STARS.

sleet_krkn [62]

Hello there,

All compounds of carbon are made by <span>ionic bonding.

I Hope this helps.

~Jurgen</span>

5 0

2 years ago

Read 2 more answers

Classify the following change as physical or chemical: A match lights when struck.

mr_godi [17]

I think the answer is:
B. Chemical Change.

8 0

2 years ago

A 5.00-mL sample of blood was treated with trichloroacetic acid to precipitate proteins. After centrifugation, the resulting sol

Anarel [89]

Explanation:

According to the Beer-lambert' s law,

Absrobance = absrobptitvity × lenght × concentration

So, if we will plot a graph between absrobance and concentration then we will obtain a straight line

Hence, formula to calculate slope of the graph is as follows.

The slope of graph = $\frac{\text{difference in absrobance at two points}}{\text{difference in concentrations at those points}}$

The given data is as follows.

$A_{1}$ = 0.412 (first point)

$A_{2}$ = 0.642 (second point)

$C_{1}$ = 0.240 ppm (first point)

$C_{2}$ = 0.475 ppm (second point)

Hence, putting these values into the above formula we will calculate the value of slope as follows.

Slope = $\frac{\text{difference in absrobance at two points}}{\text{difference in concentrations at those points}}$

= $\frac{0.642 - 0.412}{0.475 - 0.240}$

= $\frac{0.23}{0.235}$

= 0.978

It is known that for the graph, line equation can be written as follows.

y = mx + c ........... (1)

where, C = intercept

m = slope

Hence, calculate the value of intercept as follows.

0.412 = $0.24 \times 0.978$ + c

c = 0.178

As it is given that the absorbance values 0.454 (the y-axis value). Therefore, putting this value into equation (1) we get the following.

y = mx + c

0.454 = $x \times 0.978$ + 0.178

0.276 = 0.978x

x = 0.282 ppm

Thus, we can conclude that the concentration of Pb in the given sample is 0.282 ppm.

3 0

3 years ago

How many grams of tris (mw 121.1) would you need to prepare 100 ml of a 100 mm tris solution? _________ grams?

Tems11 [23]

Molarity = (Mass/ molar mass) x (1/ volume of solution in Litres)

Mass = Molarity x molar mass x volume of solution in Litres

Molarity of Tris = 100 mM = 0.1 M

volume of Tris sol. = 100 mL = 0.1 L

molar mass of Tris = 121.1 g/mol

Hence,

mass of Tris = Molarity of Tris x molar mass ofTris x volume of Tris solution

= 0.1 M x 121.1 g/mol x 0.1 L

= 1.211 g

mass of Tris = 1.211 g

7 0

3 years ago

The rate of a chemical reaction may be defined as Select one: a. the time it takes for the reaction to be completed b. the chang

kaheart [24]

It is A. This is because the rate of reaction is defined as the speed at which the reactants are converted into the products.

8 0

2 years ago