A buffer system usually will need a weak acid, like H2CO3, which is carbonic acid, and a strong base, and the only compound that could figure a fairly strong base among the options given is Na2CO3. NH3 and NaHCO3 are weak bases and HF is a strong acid. Therefore the best answer will be letter A
The answer is "List 2". They're all in scientific notation, so it's easier to organize than List 1, which is in both normal notation and scientific notation.
The correct answer is B. The tendency of molecules to move toward areas of lower concentration is called diffusion. This happens when there is a concentration gradient. This is described by the Fick's laws of diffusion. Diffusion is the net movement of molecules from a higher concentration to lower concentration to achieve equilibrium.
Answer:
- m = 1,000/58.5
- b = - 1,000 / 58.5
1) Variables
- molarity: M
- density of the solution: d
- moles of NaCl: n₁
- mass of NaCl: m₁
- molar mass of NaCl: MM₁
- total volume in liters: Vt
- Volume of water in mililiters: V₂
- mass of water: m₂
2) Density of the solution: mass in grams / volume in mililiters
3) Mass of NaCl: m₁
Number of moles = mass in grams / molar mass
⇒ mass in grams = number of moles × molar mass
m₁ = n₁ × MM₁
4) Number of moles of NaCl: n₁
Molarity = number of moles / Volume of solution in liters
M = n₁ / Vt
⇒ n₁ = M × Vt
5) Substitue in the equation of m₁:
m₁ = M × Vt × MM₁
6) Substitute in the equation of density:
d = [M × Vt × MM₁ + m₂] / (1000Vt)
7) Simplify and solve for M
- d = M × Vt × MM₁ / (1000Vt) + m₂/ (1000Vt)
- d = M × MM₁ / (1000) + m₂/ (1000Vt)
Making the simplistic assumption that the dissolved NaCl(s) does not affect the volume of the solvent water means 1000Vt = V₂
- d = M × MM₁ / (1000) + m₂/ V₂
m₂/ V₂ is the density of water: 1.00 g/mL
- d = M × MM₁ / (1000) + 1.00 g/mL
- M × MM₁ / (1000) = d - 1.00 g/mL
- M = [1,000/MM₁] d - 1,000/ MM₁
8) Substituting MM₁ = 58.5 g/mol
- M = [1,000/58.5] d - [1,000/ 58.5]
Comparing with the equation Molarity = m×density + b, you obtain:
- m = 1,000/58.5
- b = - 1,000/58.5
Answer:
(E) changing temperature
Explanation:
Consider the following reversible balanced reaction:
aA+bB⇋cC+dD
If we know the molar concentrations of each of the reaction species, we can find the value of Kc using the relationship:
Kc = ([C]^c * [D]^d) / ([A]^a * [B]^b)
where:
[C] and [D] are the concentrations of the products in the equilibrium; [A] and [B] reagent concentrations in equilibrium; already; b; c and d are the stoichiometric coefficients of the balanced equation. Concentrations are commonly expressed in molarity, which has units of moles / 1
There are some important things to remember when calculating Kc:
- <em>Kc is a constant for a specific reaction at a specific temperature</em>. If you change the reaction temperature, then Kc also changes
- Pure solids and liquids, including solvents, are not considered for equilibrium expression.
- The reaction must be balanced with the written coefficients as the minimum possible integer value in order to obtain the correct value of Kc
