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AfilCa [17]
3 years ago
14

A rock has 25 percent of its original amount of potassium-40 remaining in it; potassium-40 has a half-life of 1.25 billion years

. How long ago was the rock formed? 1.25 billion years ago 2.50 billion years ago 5.00 billion years ago 6.25 billion years ago
Chemistry
1 answer:
Hunter-Best [27]3 years ago
7 0
For rock dating, the kinetics used is first-order with the equation

ln(initial conc./final conc.) = kt

First, we determine k, which is the reaction constant. With the given half-life, this means that the final conc. is half of the initial conc. Hence,

ln 2 = k (1.25 x10^7)
k =5.55 x 10^-8

Then we use this to predict the time elapsed.

ln (1/0.25) = (5.55x10^-8)(t)
t = 2.5 x 10^7 or 2.5 billion years

I hope I was able to help you with your question. Have a good day.
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One mole of which of these compounds contains two moles of hydrogen atoms? f NaOH g H2S h CH4 j NH3
Bas_tet [7]
G. H2S contains two hydrogen atoms
4 0
3 years ago
A chef plans to mix 100% vinegar with italian dressing. the italian dressing contains 13% vinegar. the chef wants to make 150 mi
charle [14.2K]
To determine the volume of both concentration of vinegar, we need to set up two equations since we have two unknowns. 

For the first equation, we do a mass balance:

mass of 100% vinegar + mass of 13% vinegar = mass of 42% vinegar

Assuming they have the same densities, then we can write this equation in terms of volume.

V(100%) + V(13%) = V(42%)
   we let x = V(100%)
             y = V(13%)

x + y = 150

For the second equation, we do a component balance:

1.00x + .13y = 150(.42)
x + .13y = 63

The two equations are
x + y = 150
x + .13y = 63

Solving for x and y,
x = 50
y = 100

Therefore, you need to mix 50 mL of the 100% vinegar and 100 mL of the 13% vinegar.

6 0
3 years ago
Calculate the equilibrium constant for the reaction using the balanced chemical equation and the concentrations of the substance
Oliga [24]

Answer:

4.75 is the equilibrium constant for the reaction.

Explanation:

CO(g)+H_2O(g)\rightleftharpoons CO_2(g)+H_2(g)

Equilibrium concentration of reactants :

[CO]=0.0590 M,[H_2O]=0.00600 M

Equilibrium concentration of products:

[CO_2]=0.0410 M,[H_2]=0.0410 M

The expression of an equilibrium constant is given by :

K_c=\frac{[CO_2][H_2]}{[CO][H_2O]}

K_c=\frac{0.0410 M\times 0.0410 M}{0.0590M\times 0.00600 M}

K_c=4.75

4.75 is the equilibrium constant for the reaction.

3 0
3 years ago
For the reaction o(g) + o2(g) → o3(g) δh o = −107.2 kj/mol given that the bond enthalpy in o2(g) is 498.7 kj/mol, calculate the
Aneli [31]
The reaction;
O(g) +O2(g)→O3(g), ΔH = sum of bond enthalpy of reactants-sum of food enthalpy of products.
ΔH = ( bond enthalpy of O(g)+bond enthalpy of O2 (g) - bond enthalpy of O3(g)
-107.2 kJ/mol = O+487.7kJ/mol =O+487.7 kJ/mol +487.7kJ/mol =594.9 kJ/mol
Bond enthalpy (BE) of O3(g) is equals to 2× bond enthalpy of O3(g) because, O3(g) has two types of bonds from its lewis structure (0-0=0).
∴2BE of O3(g) = 594.9kJ/mol
Average bond enthalpy = 594.9kJ/mol/2
=297.45kJ/mol
∴ Averange bond enthalpy of O3(g) is 297.45kJ/mol.
8 0
3 years ago
I need please fast ASAP
sdas [7]
Kindly checkout the attached pic. It contains all your required questions. 

4 0
3 years ago
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