Response:
The pKa value is 13.0.
Clarification:
pKa + pKb = 14
For trimethylamine, Kb = 6.3 × 
Calculating pKb: pKb = - log (6.3 × )
= 1.0
Thus, pKa = 14 - pKb = 14 - 1.0
pKa = 13.0
Verification: The typical range for pKa in weak acids is from 2 to 13.
Answer:
3.816 × 10⁻³ M
Explanation:
A stock solution of Cu²⁺(aq) is made by dissolving 0.8875 g of solid Cu(NO₃)₂∙2.5H₂O in a 100.0-mL volumetric flask, and then brought up to volume with water. What is the molarity (in M) of Cu²⁺(aq) in this stock solution?
We can derive the following relations:
- The molar mass of Cu(NO₃)₂∙2.5H₂O is 232.59 g/mol.
- Each mole of Cu(NO₃)₂∙2.5H₂O yields one mole of Cu²⁺.
The moles of Cu²⁺ present in 0.8875 g of Cu(NO₃)₂∙2.5H₂O are:
The molarity of Cu²⁺ is:
Response:
The mass percentage of a solution comprising 7.6 grams of sucrose and 83.4 grams of water equals 8.351 %.
Details:
Provided data:
Sucrose mass = 7.6 grams
Water mass = 83.4 grams
In this scenario, sucrose acts as the solute, while water is the solvent.
The calculation for mass percent of a solution is done using the following formula:
Mass percent = (Mass of Solute/Mass of Solution)(100)
As sucrose is the solute, the mass equals 7.6 grams.
The total mass of the solution, which includes both sucrose and water, comes out to:
Total mass = 7.6 grams + 83.4 grams = 91 grams
Therefore, applying the values gives mass percent = (7.6/91)(100) = 8.351 %.
Specific enthalpy is defined as the overall energy in a system attributed to its temperature and pressure, measured per unit mass. It is essential in thermodynamic calculations when one needs to determine the energy for a specific unit mass of a component.
Specific enthalpy can be computed with the equation:
H = U + PV
For this example, the specific volume is 4.684 cm³/g or 149.888 cm³/g moles, which translates to 149.888 × 10⁻³ J/g moles.
The specific internal energy (U) is 1706 J/mol, and the pressure measured is 41.64.
Calculating gives us H = 1706 + 41.64 × 149.888 × 10⁻³ × 101.3 joules
= 2428 joules / mole
Answer:
Endothermic: water formation from ice and a cold instant ice pack Explanation:
