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3 years ago

Name the stellar process in which the fusion of hydrogen produces other elements.

1 answer:

3 0

<span>Hydrogen fusion generates the energy for proton - proton chains and the carbon nitrogen oxygen cycle. It is the nuclear fusion of 4 protons to form a helium 4 nucleus.</span>

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Caffeine (C8H10N4O2) is a weak base with a pKb of 10.4. Calculate the pH of a solution containing a caffeine concentration of 41

RSB [31]

Answer:

pH → 7.47

Explanation:

Caffeine is a sort of amine, which is a weak base. Then, this pH should be higher than 7.

Caffeine + H₂O ⇄ Caffeine⁺ + OH⁻ Kb

1 mol of caffeine in water can give hydroxides and protonated caffeine.

We convert the concentration from mg/L to M

415 mg = 0.415 g

0.415 g / 194.19 g/mol = 2.14×10⁻³ mol

[Caffeine] = 2.14×10⁻³ M

Let's calculate pH. As we don't have Kb, we can obtain it from pKb.

- log Kb = pKb → 10^-pKb = Kb

10⁻¹⁰'⁴ = 3.98×10⁻¹¹

We go to equilibrium:

Caffeine + H₂O ⇄ Caffeine⁺ + OH⁻ Kb

Initially we have 2.14×10⁻³ moles of caffeine, so, after the equilibrium we may have (2.14×10⁻³ - x)

X will be the amount of protonated caffeine and OH⁻

Caffeine + H₂O ⇄ Caffeine⁺ + OH⁻ Kb

(2.14×10⁻³ - x) x x

We make the expression for Kb:

3.98×10⁻¹¹ = x² / (2.14×10⁻³ - x)

We can missed the -x in denominator, because Kb it's a very small value.

So: 3.98×10⁻¹¹ = x² / 2.14×10⁻³

√(3.98×10⁻¹¹ . 2.14×10⁻³) = x → 2.92×10⁻⁷

That's the [OH⁻]. - log [OH⁻] = pOH

- log 2.92×10⁻⁷ = 6.53 → pOH

14 - pOH = pH → 14 - 6.53 = 7.47

4 0

3 years ago

What atom has 2 electrons, 6 protons and 7 neutrons

Deffense [45]

Answer:

Carbon atoms with 7 neutrons have an atomic mass of 13 (6 protons + 7 neutrons = 13). These atoms are the isotope called carbon-13.Jul

7 0

3 years ago

The temperature of a sample of liquid water changes from 50°C to 30°C. Which statement best explains the change

KiRa [710]

Answer:

The molecules move slower than the temp of 50°c and their average kinetic energy decreases.

Explanation:

kinetic energy cannot increase as temperature is reduced. molecules will still move with reduced motion.

7 0

3 years ago

A sample of 42 mL of carbon dioxide gas was placed in a piston in order to maintain a constant 101 kPa of pressure.

Lilit [14]

Answer:

The answer to your question is 33.4 ml

Explanation:

Data

volume 1 = V1 = 42 ml

temperature 1 = T1 = 20°C

temperature 2 = T2 = -60°C

Volume 2 = V2 = x

Process

1.- Convert celsius to kelvin

T1 = 20 + 273 = 293°K

T2 = -60 + 273 = 233°K

2.- Use the Charles' law to solve this problem

$\frac{V1}{T1} = \frac{V2}{T2}$

Solve for V2

V2 = $\frac{V1T2}{T1}$

3.- Substitution

V2 = $\frac{(42)(233)}{293}$

4.- Simplification

V2 = $\frac{9786}{293}$

5.- Result

V2 = 33.4ml

3 0

3 years ago

Which statements describe the elements? Which ones are true and which ones are false?

Alchen [17]

Answer:

Explanation:

Uma declaração verdade é identificada pelo de ela afirmar a verdade diferente das outras opções

8 0

3 years ago