Answer:
C. Magnetization of iron
Explanation:
This is a chemical change and cannot be undone by physical means therefore it isn't a physical change
Answer:
C. CH₄ is less than NH₃ because the NH bond is more polar than the CH bond
Explanation:
The intermolecular forces between ammonia is far stronger than for methane. Between the molecules of ammonia we have the presence of hydrogen bonds. This bond is absent in methane.
Hydrogen bonds are one of the strongest intermolecular forces. It is as a result of the electrostatic attraction between the hydrogen atom of one molecule and the electronegative atom N, O and F of another molecule.
- This strong interaction is absent in methane which has just dipole - dipole attraction.
The strength of the hydrogen bond depends on the electronegativity of the combining atoms.
Answer:
0.218 M of Pb(NO3)2
Explanation:
Equation of the reaction
Pb(NO3)2(aq) + 2NaCl(aq) --> PbCl2(s) + 2NaNO3(aq)
1 mole of Pb(NO3)2 reacts to precipitate 1 mole of PbCl2
Molar mass of PbCl2 = 207 + (35.5*2)
= 278 g/mol
Number of moles of PbCl2 precipitated = mass/molar mass
= 12.11/278
= 0.04356 mol
Since 0.04356 moles of PbCl2 was precipitated, therefore by stoichiometry; 0.04356 moles of Pb(NO3)2 reacted.
Molarity is defined as the number of moles of solute in 1 liter of solution.
Molarity = number of moles/volumes
= 0.04356/0.2
= 0.218 M
Answer:
A) Dilute the unknown so that it will have an absorbance within the standard curve. Once the diluted unknown concentration is determined, the full strength concentration can be calculated if the dilution process is recorded. Beer's law only applies to dilute solutions, so diluting the unknown is better than making new standards.
Explanation:
Beer's law states that <em>absorbance is proportional to the concentrations of the absorbing species</em>. This is verified in the case of diluted solutions (0≤0.01 M) of most substances. <u>As a solution gets more concentrated, solute molecules interact between themselves because of their proximity. </u>When a molecule interacts with another, the change in their electric properties (including absorbance) is probable. That's why <u>the plot of absorbance versus concentration stops being a straight line</u>, and <u>Beer's law is no longer valid.</u>
Therefore, if the absorbance value is higher than the highest standard, dilutions should be made. Once this concentration is determined, the full strength concentration can be calculated with the inverse of the dilution.
