Answer:
Dark matter makes up 85% of the mass of the universe. Dark matter is not directly observable because it doesn't interact with any electromagnetic wave. In the development of the universe, without dark matter, the universe will not function, move or rotate as it does now (this speculation led to the quest to find the anomaly of mass and energy in the known universe, eventually leading to the idealization of dark matter) and will not have enough gravitational force to hold it together. After the big bang,<em> the presence of dark matter and energy ensured that the newly formed universe didn't just float away, rather, it provided enough gravitational force to hold the universe while still allowing it to expand sufficiently</em>.
The development of the universe would have been different without the universe in the sense that the young universe won't have enough mass to hold it together, and the universe would have simply floated apart. The behavior of the universe would have been different from what we observe now, and some physical laws that applies now will not apply to the universe.
One of the best buffer choice for pH = 8.0 is Tris with Ka value of 6.3 x 10^-9.
To support this answer, we first calculate for the pKa value as the negative logarithm of the Ka value:
pKa = -log Ka
For Tris, which is an abbreviation for 2-Amino-2-hydroxymethyl-propane-1,3 -diol and has a Ka value of 6.3 x 10^-9, the pKa is
pKa = -log Ka
= -log (6.3x10^-9)
= 8.2
We know that buffers work best when pH is equal to pKa:
pKa = 8.2 = pH
Therefore Tris would be a best buffer at pH = 8.0.
When solid carbon reacts with oxygen gas to produce carbon dioxide gas. the deltaH (enthalpy change ) value is negative .DeltaH would be on the product side of the equation.
<h3>What is enthalpy change? </h3>
In a thermodynamic system, energy is measured by enthalpy. Enthalpy is a measure of a system's overall heat content and is equal to the system's internal energy plus the sum of its volume and pressure.
Knowing whether q is endothermic or exothermic allows one to characterise the relationship between q and H. An endothermic reaction is one that absorbs heat and demonstrates that heat from the environment is used in the reaction, hence q>0 (positive). For the aforementioned equation, under constant pressure and temperature, if q is positive, then H will also be positive. In a similar manner, heat is transferred to the environment when it is released during an exothermic reaction. Thus, q=0 (negative). Therefore, if q is negative, H will also be negative.
Learn more about enthalpy change here :
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Answer:
strength = 10⁻²/10⁻³ = 10 times more acidic
Explanation:
1. A solution with a pH of 9 has a pOH of
pH + pOH = 14 => pOH = 14 - pH = 14 - 9 = 5
2. Which is more acidic, a solution with a pH of 6 or a pH of 4?
pH of 4 => Higher [H⁺] = 10⁻⁴M vs pH of 6 => [H⁺] = 10⁻⁶M
3. How many times more acidic is a solution with a pH of 2 than a solution with a pH of 3?
soln with pH = 2 => [H⁺] = 10⁻²M
soln with pH = 3 => [H⁺] = 10⁻³M
strength = 10⁻²/10⁻³ = 10 times more acidic
4. What is the hydrogen ion concentration [H + ] in a solution that has a pH of 8?
[H⁺] = 10^-pH = 10⁻⁸M
5. A solution has a pOH of 9.6. What is the pH? (Use the formula.)
pH + pOH = 14 => pH = 14 - 9.6 = 4.4
<span>Chemical reaction: CH</span>₃COO⁻(aq) + H⁺(aq) ⇄ CH₃COOH(aq).
H⁺ is from HNO₃: HNO₃ → H⁺ + NO₃⁻.
<span>A buffer can
be defined as a substance that prevents the pH of a solution from changing by
either releasing or absorbing H</span>⁺ in a
solution.
Buffer is a solution
that can resist pH change upon the addition of an acidic or basic components
and it is able to neutralize small amounts of added acid or base, pH of
the solution is relatively stable.
