Which of the following solutions would make a good buffer system? (Check all that apply.) A. A solution that is 0.10 M NH3 and 0.10 M NH4Cl B. A solution that is 0.10 M HCN and 0.10 M NaF C. A solution that is 0.10 M HCN and 0.10 M LiCN D. A solution that is 0.10 M HF and 0.10 M NaF
Answers
Answer:
A solution that is 0.10 M HCN and 0.10 M LiCN
. A solution that is 0.10 M NH3 and 0.10 M NH4Cl
Explanation:
A buffer consists of a weak acid and its conjugate base counterpart. HCN is a weak acid and the salt LiCN contains its counterpart conjugate base which is the cyanide ion. A buffer maintains the pH by guarding against changes in acidity or alkalinity of the solution.
A solution of ammonium chloride and ammonia will also act as a basic buffer. A buffer may also contain a weak base and its conjugate acid.
Answer:
Good buffer systems are:
A) NH3 + NH4Cl
C) HCN + LiCN
D) HF + NaF
Explanation:
Buffers consist in a mixture of a weak acid with its salt or a weak alkaly with its salt. All buffer systems are conformed by:
1) Weak acid + salt
or
2) Weak alkaly + salt
It is very important these salts come from the weak acid or weak alkaly. It means, the anion of the acid must be the anion in the salt which is going to be part of the buffer system. On the other hand, the cation of the weak alkaly must be the cation of the salt which is going to form the salt in the buffer system.
Then, when we evaluate all options in this exercise, answers are the following:
A) 0.10 M NH3 and 0.10 M NH4Cl. It is a buffer because NH3 (ammonia) is a weak alkaly and NH4Cl is a salt coming from NH3.
Buffer component reactions:
Reaction weak alkaly: NH3 + H2O <-----> NH4+ + OH-
Reaction salt in water: NH4Cl ---> NH4+ + Cl-
NH4+ is the cation of the weak alkaly so it must be part of the salt in the buffer system. Then NH4Cl is a salt from NH3.
C) 0.10 M HCN and 0.10 M LiCN. It is a buffer because HCN is a weak acid and LiCN is a salt which is coming from HCN.
Buffer component reactions:
Reaction weak acid: HCN + H2O <-----> H3O+ + CN-
Reaction salt in water: LiCN --> Li+ + CN-
CN- is the anion of the acid, so it must be part of the salt in the buffer system. Then LiCN is a salt from HCN.
D) 0.10 M HF and 0.10 M NaF. It is a buffer because HF is a weak acid and NaF is a salt which is coming from HF.
Buffer component reactions:
Reaction weak acid: HF + H2O <------> H3O+ + F-
Reaction salt in water: NaF ---> Na+ + F-
F- is the anion of the weak acid (HF), so it must be part of the salt in th buffer systema. Then NaF is a salt coming from HF.
However option B, it is not a buffer, because it is a mixture of 0.10 M HCN and 0.10 M NaF. Salt is not coming from the weak acid.
Reaction weak acid: HCN + H2O <-----> H3O+ + CN- (anion of the acid is CN-)
Rection salt in water: NaF --> Na+ + F- (anion in the salt is F-, not CN-)
Anion of the acid is CN- and the anion in the salt is F- so it is not a salt coming from the weak acid. Then option B it is not a buffer system.
Related Questions
Calculate the solubilities of the following compounds in a 0.02 M solution of barium nitrate using molar concentrations, first ignoring ionic strength and activities. a. silver iodate b. barium sulfate c. Repeat the above calculations using ionic strength and activities.
A construction worker is transporting pieces of plastic in two stacks with touching pieces. In Stack 1, both pieces of plastic are the same size. In Stack 2, the bottom piece is the same size as those in Stack 1, and the top piece is larger. The diagram above shows the energy of the molecules in the pieces of plastic before they touched.After a while, which of the two top plastic pieces will be cooler, and why?
What is the freezing point (°C) of a solution prepared by dissolving 11.3 g of Ca(NO3)2 (formula weight = 164 g/mol) in 115 g of water? The molal freezing point depression constant for water is 1.86 °C/m.
Write the equation for the alpha decay of C-11. Write the equation for the beta decay of Be-10HELP HELP HELP
Answers
Answer : The number of drops pf the stock solution mist be added are, 50 drops.
Explanation :
As we are given that the concentration of stock solution 1 mg/mL and pipette delivers 20 drops/mL. That means,
1 mg of epinephrine = 1 mL = 20 drops
The final volume of Locke's solution = 25 mL
and the final concentration needed =
As, 1 mL of solution contains =
So, 25 mL of solution contains =
Conversion used :
Now we have to determine the number of drops needed.
As, 1 mg of epinephrine contains 20 drops.
So, 2.5 mg of epinephrine contains 2.5 × 20 = 50 drops.
Therefore, the number of drops pf the stock solution mist be added are, 50 drops.
Final answer:
If you want to achieve a final concentration of 100 µg/mL of epinephrine in a 25 mL solution, when using a stock solution of 1 mg/mL and a pipette that delivers 20 drops/mL, you need to add 50 drops of your stock solution.
Explanation:
Since we are asked to find the number of drops of stock solution required to achieve a final concentration of 100 µg/mL in a 25 mL solution, the first step is to convert the concentration of the stock solution to the same units, µg/mL. Hence, 1 mg/mL is equal to 1000 µg/mL. Further, we know that 1 mL of the stock solution contains 1000 µg of epinephrine, and our pipette delivers 20 drops/mL, so 1 drop of stock solution contains 1000 µg / 20 drops = 50 µg. Thus, if we need a 100 µg/mL concentration in 25 mL, we need a total of 100 µg/mL * 25 mL = 2500 µg of epinephrine. Therefore, to achieve this, we must add 2500 µg / 50 µg/drop = 50 drops of our stock solution. Hence,
50 drops
of the stock solution should be added to achieve the desired concentration.
Learn more about Solution Dilution here:
#SPJ12
Answers
Here's the answer, I remember doing this problem last year.
23.5 degrees north, 77 degrees west
Answers
Answers
Answer:
3.11 mol/kg
Explanation:
Molality M = number of moles of solute, n/mass of solvent, m
To calculate the number of moles of glycerol (C₃H₈O₃) in 22.75 g of glycerol, we find its molar (molecular) mass, M',
So, M' = 3 × atomic mass of carbon + 8 × atomic mass hydrogen + 3 × atomic mass of oxygen
= 3 × 12 g/mol + 8 × 1 g/mol + 3 × 16 g/mol = 36 g/mol + 8 g/mol + 48 g/mol = 92 g/mol.
So, number of moles of glycerol, n = m'/M' where m' = mass of glycerol = 22.75 g and M' = molecular mass of glycerol = 92 g/mol
So, n = m'/M'
n = 22.75 g/92 g/mol
n = 0.247 mol
So, the molality of the solution M = n/m
Since m = mass of ethanol = 79.6 g = 0.0796 kg, substituting the value of n into the equation, we have
M = 0.247 mol/0.0796 kg
M = 3.11 mol/kg
So, the molality of the solution is 3.11 mol/kg.
One mole of carbon would contain 6.02 x 1023 carbon atoms, but one mole of chlorine would contain 6.02 x 1023 diatomic chlorine molecules.
For ionic compounds, the representative particle is the formula unit of the compound (eg. NaCl).
One mole of water (H2O) contains 6.02 x 1023 atoms.
Avogadro's number is the number of discrete, representative units found in one mole of a substance.
Answers
Answer:
Option C
Explanation:
Avogadro number represent discrete unit of a substance which can be atom, molecule, ion etc.
In one mole of H2O there will be 6.02 x 1023 molecules and not atoms.
Molecule of H2O is the discrete unit of water mole and not atom.
Hence, option C is correct choice of answer
Answers
Whereas, the system under study is absorbing heat that is produced during the reaction. So if ΔH is found to be positive then it can be called as endothermic reaction.
The enthalpy change of the reaction indicates that it is an endothermic process.
FURTHER EXPLANATION
Enthalpy (ΔH) is the amount of heat absorbed or released in a reaction. It is based on the amount of energy needed to break the bonds and the energy released during bond formation. Enthalpy change is the difference in the enthalpy of the reactants and the products. The positive or negative sign for an enthalpy value indicates the direction of the heat flow: a positive ΔH indicates that the reaction is endothermic while a negative value for ΔH means that the reaction is exothermic.
Endothermic Reactions
Endothermic reactions are reactions that absorb heat from the surroundings to the system. This is the case when more energy is absorbed to break the bonds than is released to form the bonds. Endothermic reactions can be identified in the lab by observing if the reaction vessel becomes cooler as the reaction proceeds.
Exothermic Reactions
When the amount of energy released during bond formation is greater than the amount of energy absorbed during bond breaking, a net release of energy to the surroundings takes place and the reaction is exothermic. Exothermic reactions can be identified when the reaction vessel becomes hot as the reaction progresses.
LEARN MORE
- Heat capacity brainly.com/question/12976104
- Equilibrium brainly.com/question/12983923
- Gibbs Free Energy brainly.com/question/12979420
Keywords: Endothermic, Exothermic, Enthalpy