please help its due at 2

Answer: The footprints were made [tex]2.99\times 10^6years[/tex] years long ago.

Explanation:

Radioactive decay follows first order kinetics.

Half-life of isotope X= 500,000 years

[tex]\lambda =\frac{0.693}{t_{\frac{1}{2}}}=\frac{0.693}{500000}=0.00000139year^{-1}[/tex]

The equation for first order kinetics is :

[tex]N=N_o\times e^{-\lambda t}[/tex]

N = amount left after time t  = 0.125 mg

[tex]N_0[/tex] = initial amount  = 8.00 mg

[tex]\lambda[/tex] = rate constant

t= time  

Putting the values we get:

[tex]0.125=8.00\times e^{- 0.00000139years^{-1}\times t}[/tex]

[tex]0.0156=e^{- 0.00000139years^{-1}\times t}[/tex]

[tex]t=2.99\times 10^6years[/tex]

The footprints were made [tex]2.99\times 10^6years[/tex] years long ago.

Answer:

Follows are the solution:

Explanation:

A + B = C

Its response decreases over time as well as consumption of a reactants.  

r = -kAB

during response A convert into 2x while B convert into x to form 3x of C

let's  y = C

y = 3x

Still not converted sum of reaction  

for A: 100 - 2x

for B: 50 - x

Shift of x over time  

[tex]\frac{dx}{dt} = \frac{-k(100 - 2x)}{(50 - x)}[/tex]

Integration of x as regards t  

[tex]\frac{1}{[(100 - 2x)(50 - x)]} dx = -k dt\\\\\frac{1}{2[(50 - x)(50 - x)]} dx = -k dt\\\\\ integral\ \frac{1}{2[(50 - x)^2]} dx =\ integral [-k ] \ dt\\\\\frac{-1}{[100-2x]} = -kt + D \\\\[/tex]

D is the constant of integration

initial conditions: t = 0, x = 0

[tex]\frac{-1}{[100-2x]} = -kt + D \\\\\frac{ -1}{[100]} = 0 + D\\\\D= \frac{-1}{100}\\\\[/tex]

hence we get:

[tex]\frac{-1}{[100-2x]}= -kt -\frac{1}{100}\\\\or \\\\ \frac{1}{(100-2x)} = kt + \frac{1}{100}[/tex]

after t = 7 minutes , [tex]C = 10 \ g = 3x[/tex]

[tex]3x = 10\\\\x = \frac{10}{3}[/tex]

Insert the above value x into [tex]\frac{1}{(100-2x)}[/tex] equation [tex]= kt + \frac{1}{100}[/tex] to get k.  

[tex]\to \frac{1}{(100-2\times \frac{10}{3})} = k \times (7) + \frac{1}{100} \\\\ \to \frac{1}{(100- 2 \times 3.33)} = \frac{700k + 1}{100} \\\\ \to \frac{1}{(100-6.66)} = \frac{700k + 1}{100}\\\\ \to \frac{1}{93.34} = \frac{700k + 1}{100} \\\\[/tex]

[tex]\to 100 = 93.34(700k + 1) \\\\ \to 100 = 65,338k + 700 \\\\ \to 65,338k = -600 \\\\ \to k = \frac{-600}{ 65,338} \\\\ \to k= - 0.0091[/tex]

therefore plugging in the equation the above value of k  

[tex]\to \frac{1}{(100-2x)} = kt +\frac{1}{100} \\\\\to \frac{1}{(100-2x)} = -0.0091t + \frac{1}{100}\\\\\to \frac{1}{(100-2x)} = \frac{1 -0.91t}{100}\\\\\to \frac{1}{2(50-x)} = \frac{1 -0.91t}{100}\\\\\to \frac{1}{(50-x)} = \frac{1 -0.91t}{50}\\\\\to 50= (1-0.91t)(50-x)\\\\\to 50 = 50-45.5t-x-0.91tx\\\\\to x+0.91xt= -45.5t\\\\\to x(1+0.91t)= -45.5t\\\\\to x=\frac{-45.5t}{1+0.91t}[/tex]

Let y = C

, calculate C:

y = 3x

[tex]y =3 \times \frac{-45.5t}{1+0.91t}[/tex]

amount of C formed in 28 mins

[tex]x = \frac{-45.5t}{1+0.91t} ,[/tex] plug t = 28

[tex]\to x = \frac{-1274}{1+25.48} \\\\\to x = \frac{-1274}{26.48} \\\\\to x= -48.26[/tex]

therefore amount of C formed in 28 minutes is = 3x = 144.78 grams

C: [tex]y =3 \times \frac{-45.5t}{1+0.91t}[/tex]

y= 136.5 =137

Explanation:

NH₃ has only two non-binding pairs (lone pairs) of e⁻ in it's Lewis structure.

••

H—N—H

|

H

Therefore,

C is correct. ✔

Answer:

The goal of science is to learn how nature works by observing the natural and physical world, and to understand this world through research and experimentation.

Explanation:

Answer:

balance for the 1st and mass for the 2nd

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I think the answer is true

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Explanation:

Gravity is what holds the planets in orbit around the sun and what keeps the moon in orbit around Earth. ... Gravity creates stars and planets by pulling together the material from which they are made. Gravity not only pulls on mass but also on light.

Answer:If you help me with the triple beam balance gizmo then i can do this for you

Explanation:please i need help

Answer:

Friction

Explanation:

Energy is lost to heat as the object overcomes kinetic friction as it slides up the ramp. The energy loss is equal to the work done by the friction force.

Answer:

30

Explanation:

its pushed into a 30 resistor

Answer:

No, this is invalid. The term mono in front of monoatomic simply refers to the number of atoms that are present in a compound or simply by itself it has no relationship with respect to the overall charge of the compound.

Explanation:

For instance Ca is considered as a monoatomic ion but it has a charge of +2.

Answer:

1.5 x 10⁵

Explanation:

Scientific notation always starts in the 1's place (1.)

Answer:

Sabihin mo

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salamat shoppe

Answer:

t

Explanation:

because for atoms to change they have to have some kind of chemical action to get new life

Answer:

hkile uo gihme rapre

Explanation:

Answer:

The expression of speed of light can be written as "c".

Explanation:

The speed of light is denoted by c. It is originated from the Latin word celeritas which means "speed".  Its value is 3×10⁸ m/s.

It is related to the frequency and wavelength as follow,

Speed of light = wavelength × frequency

c = λ × f

λ = c/f

This formula shows that both frequency ad wavelength are inversely related to each other.

Frequency is taken in Hz.

It is the number of oscillations, wave of light make in one second.

Wavelength is designated as "λ" and it is the measured in meter. It is the distance between the two crust of two trough.

Answer:

The activation energy for the forward reaction is the amount of free energy that must be added to go from the energy level of the reactants to the energy level of the transition state. ... Once a reactant molecule absorbs enough energy to reach the transition state, it can proceed through the remainder of the reaction.

Explanation:

Answer: Activation energy is how much energy it takes for a reaction to occur.

Explanation:

Answer:

1.) Genetic Variation, 2.) reproduction doesn't require a mate.

Explanation:

These are the only two that actually make sense in the blanks, So trust me or trust the other two answers.Your choice.

Answer:

cation

Explanation:

a cation is an ion with a postitive charge. This (cat)ion (+) = cats are good , anion (onion) are not good (-)

Answer:

Plumbing System

Explanation:

Answer:

C plumbing system

Explanation:

Infrastructure is the basic structures needed for the operation of society

as distance from nucleus increases , energy of shells also increases

Answer:

Cl^- = 5.75

K^+ = 7.75

Explanation:

Now let us calculate the effective nuclear charge four K^+ and Cl^- from Slater's rule.

Given that Cl^- and K^+ has electronic configuration of; [Ne] 3s2 3p6 (they are isoelectronic species)

We compute S as follows;

For n - 2 level, S= 1

For n - 1 level, S= 0.85

For ns,np level S= 0.35

Note: S= screening or shielding constant

1s2, S=2 ×1 = 2

2s2 2p6, S= 8×0.85 = 6.8

3s2 3p6, S= 7 × 0.35 = 2.45

The electron under study is not considered hence seven out of eight electrons in the shell are considered

Hence

S= 2 + 6.8 + 2.45 = 11.25

Since Cl^- has 17 electrons;

Zeff(Cl^-) = 17 - 11.25 = 5.75

For K^+

Zeff = 19 - 11.25 = 7.75

Answer:

It would be compound.

Explanation:

It is this way because if it adds another proton it becomes more positive that nuetral, and if you add an electron it just makes the atom more dense. That is why the answer is compound. Hope this helped :)

Answer:

difficile infection. By reintroducing a healthy diversity of bacteria, fecal transplantation can re-establish colonization resistance to prevent C. difficile from gaining a foothold and becoming a dominant organism in the environment of the gut.

Explanation:

Answer:

Its D :)

Or not i haven't done this in a while-

Answer:

compound

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your answer would be compound

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compound

Explanation:

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a

Explanation:

Answer:A. When particles transfer energy by touching.

Example: After a car is turned on, the engine becomes hot.