Calculate (1/2)^2.6*100%

While exploring a coal mine, scientists found plant fossils in the ceiling of the mine which had been preserved by an earthquake

ale4655 [162]

Answer:

11552.45 years

Explanation:

Given that:

Half life = 5730 years

$t_{1/2}=\frac{\ln2}{k}$

Where, k is rate constant

So,

$k=\frac{\ln2}{t_{1/2}}$

$k=\frac{\ln2}{5730}\ years^{-1}$

The rate constant, k = 0.00012 years⁻¹

Using integrated rate law for first order kinetics as:

$[A_t]=[A_0]e^{-kt}$

Where,

$[A_t]$ is the concentration at time t

$[A_0]$ is the initial concentration

Given that:

The rate constant, k = 0.00012 years⁻¹

Initial concentration $[A_0]$ = 160.0 counts/min

Final concentration $[A_t]$ = 40.0 counts/min

Time = ?

Applying in the above equation, we get that:-

$40.0=160.0e^{-0.00012\times t}$

$e^{-0.00012t}=\frac{1}{4}$

$-0.00012t=\ln \left(\frac{1}{4}\right)$

$t=11552.45\ years$

7 0

2 years ago

What is the molarity of a solution that contains 122g of MgSO4 n 3.5L of solution?

Semmy [17]

Answer:

0.29mol/L or 0.29moldm⁻³

Explanation:

Given parameters:

Mass of MgSO₄ = 122g

Volume of solution = 3.5L

Molarity is simply the concentration of substances in a solution.

Molarity = number of moles/ Volume

>>>>To calculate the Molarity of MgSO₄ we find the number of moles using the mass of MgSO₄ given.

Number of moles = mass/ molar mass

Molar mass of MgSO₄:

Atomic masses: Mg = 24g

S = 32g

O = 16g

Molar mass of MgSO₄ = [24 + 32 + (16x4)]g/mol

= (24 + 32 + 64)g/mol

= 120g/mol

Number of moles = 122/120 = 1.02mol

>>>> From the given number of moles we can evaluate the Molarity using this equation:

Molarity = number of moles/ Volume

Molarity of MgSO₄ = 1.02mol/3.5L

= 0.29mol/L

IL = 1dm³

The Molarity of MgSO₄ = 0.29moldm⁻³

8 0

3 years ago

A valid lewis structure of __________ cannot be drawn without violating the octet rule. a valid lewis structure of __________ ca

Oxana [17]

A valid Lewis structure of IF3 cannot be drawn without violating the octet rule.

Answer: IF3 (Iodine Trifluoride)

This is because, I (Iodine) and F (Fluorine) both have odd number of valence electrons (7) which also means that there are too many valence electrons in the valence shell.

5 0

3 years ago

Hellllpppppppp helppppppppp

mixas84 [53]

Answer :

Charles's Law : It is defined as the volume is directly proportional to the temperature of the gas at constant pressure and number of moles.

Mathematically,

$V\propto T$

Boiling water bath Cool bath 1 Cool bath 2

Temperature (⁰C) 99 17 2

Temperature (K)(T) 273+99=372 273+17=290 273+2=275

Volume of water 0.0 27.0 34.0

in cool flask (mL)

Volume of water= 135.8 135.8 135.8

Air in flask (mL)

Volume of air 135.8 108.8 101.8

in cool flask (V)

$\frac{V}{T}$ $\frac{135.8}{372}=0.365$ $\frac{108.8}{290}=0.375$ $\frac{101.8}{275}=0.370$

The graph volume versus temperature for a gas is shown below.

3 0

2 years ago

How many moles (of molecules or formula units) are in each sample? 79.34 g cf2cl2?

Alona [7]

From the periodic table:
molecular mass of carbon = 12 grams
molecular mass of fluorine = 18.99 grams
molecular mass of chlorine = 35.5 grams
Therefore:
one mole of CF2Cl2 = 12 + 2(18.99) + 2(35.5) = 120.98 grams
Therefore, we can use cross multiplication to find the number of moles in 79.34 grams as follows:
mass = (79.34 x 1) / 120.98 = 0.6558 moles

Now, one mole contains 6.022 x 10^23 molecules, therefore:
number of molecules in 0.65548 moles = 0.6558 x 6.022 x 10^23
= 3.949 x 10^23 molecules

7 0

2 years ago