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1 year ago

Which of the following statements is one

Chemistry

1 answer:

elena-14-01-66 [18.8K]1 year ago

7 0

Answer:

a. All elements are composed of atoms.

Explanation:

dalton's atomic theory says that Compounds are composed of atoms of more than 1 element. The relative number of atoms of each element in a given compound is always the same. Chemical reactions only involve the rearrangement of atoms. Atoms are not created or destroyed during chemical reactions.

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I'm redoing the Heat of Combustion Lab for a better grade and I REALLY need the answers and work for all questions! PLEASE!

I am Lyosha [343]

Answer:

Hi, what are the problems on the lab?

Explanation:

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2 years ago

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

If 200 ml of 0.15 M propionic acid (PA) is added to 300 ml of 0.02 M NaOH, what is the resulting pH of the solution? Round the a

vodomira [7]

Answer:

pH = 4.543

Explanation:

CH3CH2COOH + H2O ↔ CH3CH2COO- + H3O+
pKa = - Log Ka

∴ Ka = [H3O+][CH3CH2COO-]/[CH3CH2COOH]

∴ pKa = 4.87

⇒ Ka = 1.349 E-5 = [H3O+][CH3CH2COO-]/[CH3CH2COOH]

added 300 mL 0f 0.02 M NaOH:

⇒ C CH3CH2COOH = ((0.200 L)(0.15 M)) - ((0.300 L)(0.02 M))/(0.3 + 0.2)

⇒ C CH3CH2COOH = 0.048 M

⇒ C NaOH = (0.300 L)(0.02 M) / (0.3 +0.2) = 0.012 M

mass balance:

⇒ 0.048 + 0.012 = 0.06 M = [CH3CH2COO-] + [CH3CH2COOH].......(1)

charge balance:

⇒ [H3O+] + [Na+] = [CH3CH2COO-]

∴ [Na+] = 0.02 M

⇒ [CH3CH2COO-] = [H3O+] + 0.02 M.............(2)

(2) in (1):

⇒ [CH3CH2COOH] = 0.06 M - 0.02 M - [H3O+] = 0.04 M - [H3O+]

replacing in Ka:

⇒ 1.349 E-5 = [H3O+][([H3O+] + 0.02) / (0.04 - [H3O+])

⇒ (1.349 E-5)(0.04 - [H3O+]) = [H3O+]² + 0.02[H3O+]

⇒ 5.396 E-7 - 1.349 E-5[H3O+] = [H3O+]² + 0.02[H3O+]

⇒ [H3O+]² + 0.02001[H3O+] - 5.396 E-7 = 0

⇒ [H3O+ ] = 2.867 E-5 M

∴ pH = - Log [H3O+]

⇒ pH = 4.543

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2 years ago

If a clot were made up of a mass of proteins, what change in the proteins led to the formation of a clot?

S_A_V [24]

Answer: The proteins were no longer soluble in the blood.

3 0

2 years ago

Increasing temperature makes a

LenKa [72]

Answer:

High temperature increases the number of high energy collisions

Explanation:

Increasing the temperature a reaction takes place at increases the rate of reaction. At higher temperatures, particles can collide more often and with more energy, which makes the reaction take place more quickly.

5 0

2 years ago