1. Which solution has the lowest pH?
a. 0.0045 M C6H5COOH (Ka=6.3x10-5)
b. 0.00018 M HNO3
c. 0.016 M H2CO3 (Ka1=4.3x10-7) ***
d. 0.00075 M HCOOH (Ka=1.8x10-4)
*The pH I calculated: a. 2.3, b. 3.7, c. 1.8, d. 3.1
2. In the equilibrium, F-(aq)+HO2CCO2H(aq)⇄HF(aq)+HO2CCOO-(aq), the conjugate base is
a. F- ***
b. HO2CCO2H
c. HF
d. HO2CCOO-
3. Which of the following is a Brønsted-Lowry acid-base reaction?
a. 2Na(s)+2H2O(l)⇄2NaOH(aq)+H2(g)
b. NH4^+(aq)+H2O(l)⇄NH3(aq)+H3O^+(aq) ***
c. NaHCO3(aq)+2HCl(aq)⇄NaCl(aq)+H2O(l)+CO2(g)
d. AgNO3(aq)+NaCl(aq)⇄AgCl(s)+NaNO3(aq)
I agree with 2 and 3 but not 1.
I didn't calculate all the way for the acids but the answer you have for a I don't think is right. Neither is the answer for c. b and d are OK.
oops. On #2, F^- is the base in the reaction. The CONJUCATE base is d.
In #3. the equation you have written is not correct. It isn't balanced. If it were balanced it would be
NaHCO3 + HCl ==> H2CO3 + 2NaCl in which case the HCO3]^- accepts a proton from the HCl so the HCl is an acid and the [HCO3]^- is a base in the B and L theory. Now if we take your equation and say that the 2HCl is just extra HCl, so that's a B and L acid/base also with some extra HCl thrown in. In the above reaction I wrote, the H2CO3 is not stable and gives => H2O + CO2. If you write the intermediate step I think you call it a Bronsted-Lowry acid/base rxn. If you don't go through the intermediate step I think it is not.
1. To determine which solution has the lowest pH, we need to compare their acidic strengths. The lower the pH, the stronger the acidity.
a. 0.0045 M C6H5COOH (Ka=6.3x10^-5): The value of Ka is relatively small, indicating a weak acid. The pH can be calculated using the formula pH = -log[H+]. Taking the negative logarithm of the concentration of H+ ions gives us a pH of approximately 2.3.
b. 0.00018 M HNO3: Nitric acid (HNO3) is a strong acid that dissociates completely in water. Since it is a strong acid, the concentration of H+ ions is equivalent to the concentration of the acid. So, the pH can be calculated as pH = -log[H+]. Taking the negative logarithm of 0.00018 gives us a pH of approximately 3.7.
c. 0.016 M H2CO3 (Ka1=4.3x10^-7): Carbonic acid (H2CO3) is a weak acid. Using the Ka value, we can calculate the concentration of H+ ions. pH = -log[H+]. Taking the negative logarithm of the concentration of H+ ions gives us a pH of approximately 1.8.
d. 0.00075 M HCOOH (Ka=1.8x10^-4): Formic acid (HCOOH) is a weak acid, and we can calculate the concentration of H+ ions using the Ka value. pH = -log[H+]. Taking the negative logarithm of the concentration of H+ ions gives us a pH of approximately 3.1.
Therefore, the solution with the lowest pH is option c, 0.016 M H2CO3.
2. In the equilibrium, F-(aq) + HO2CCO2H(aq) ⇄ HF(aq) + HO2CCOO-(aq), the conjugate base is the species formed when an acid loses a proton (H+). In this reaction, F-(aq) loses a proton and becomes HF(aq). Therefore, the conjugate base is option a, F-.
3. A Brønsted-Lowry acid-base reaction involves the transfer of a proton (H+ ion) from one species to another.
a. 2Na(s) + 2H2O(l) ⇄ 2NaOH(aq) + H2(g) is not a Brønsted-Lowry acid-base reaction because there is no proton transfer.
b. NH4+(aq) + H2O(l) ⇄ NH3(aq) + H3O+(aq) involves the transfer of the proton from H2O to NH4+. Therefore, this is a Brønsted-Lowry acid-base reaction.
c. NaHCO3(aq) + 2HCl(aq) ⇄ NaCl(aq) + H2O(l) + CO2(g) is a neutralization reaction, not a proton transfer, so it is not a Brønsted-Lowry acid-base reaction.
d. AgNO3(aq) + NaCl(aq) ⇄ AgCl(s) + NaNO3(aq) is a precipitation reaction, not involving proton transfer, so it is not a Brønsted-Lowry acid-base reaction.
Therefore, the answer is b, NH4+(aq) + H2O(l) ⇄ NH3(aq) + H3O+(aq) is a Brønsted-Lowry acid-base reaction.
1. To determine which solution has the lowest pH, you can compare the values of Ka (acid dissociation constant) for each of the given substances. The lower the value of Ka, the weaker the acid and the higher the pH will be.
a. 0.0045 M C6H5COOH (Ka=6.3x10-5): To calculate the pH of this solution, you can use the Ka value and the equation pH = -log[H+]. Plugging in the Ka value, we get -log(6.3x10-5) ≈ 4.2, which is the pH of this solution.
b. 0.00018 M HNO3: Since HNO3 is a strong acid, it fully dissociates in water and produces H+ ions. Therefore, the concentration of H+ ions is equal to the concentration of HNO3. Using the equation pH = -log[H+], the pH of this solution is -log(0.00018) ≈ 3.7.
c. 0.016 M H2CO3 (Ka1=4.3x10-7): H2CO3 is a weak acid that undergoes partial dissociation. To calculate the pH, we need to find the concentration of H+ ions using the Ka value. Since the concentration of H+ ions is equal to the concentration of H2CO3 that has dissociated, we can assume it is significantly smaller than the initial concentration. This approximation allows us to neglect the contribution of the dissociated H+ ions from water. Therefore, the concentration of H+ ions is approximately equal to the concentration of the dissociated H2CO3, which is 0.016 x Ka1 = 0.016 x (4.3x10-7) ≈ 6.9x10-9 M. Taking the logarithm of this concentration, we get a pH of approximately 1.8.
d. 0.00075 M HCOOH (Ka=1.8x10-4): Similar to the previous case, we can calculate the pH by finding the concentration of H+ ions using the Ka value. The concentration of H+ ions is equal to the concentration of the dissociated HCOOH, which is 0.00075 x Ka = 0.00075 x (1.8x10-4) ≈ 1.35x10-7 M. Taking the logarithm of this concentration, we get a pH of approximately 3.1.
Comparing the pH values, the solution c. 0.016 M H2CO3 (Ka1=4.3x10-7) has the lowest pH of approximately 1.8.
2. In the equilibrium, F-(aq) + HO2CCO2H(aq) ⇄ HF(aq) + HO2CCOO-(aq), the conjugate base is represented by the anion on the right side of the equation. In this case, the conjugate base is HO2CCOO-(aq). Therefore, the correct answer is d. HO2CCOO-.
3. To determine which of the given reactions is a Brønsted-Lowry acid-base reaction, we need to identify the transfer of protons (H+ ions). In this case:
a. 2Na(s) + 2H2O(l) ⇄ 2NaOH(aq) + H2(g): This is a reaction between a metal (Na) and water (H2O) but does not involve any transfer of protons. It is not a Brønsted-Lowry acid-base reaction.
b. NH4+(aq) + H2O(l) ⇄ NH3(aq) + H3O+(aq): This reaction involves the transfer of a proton from H2O to NH4+. Therefore, it is a Brønsted-Lowry acid-base reaction.
c. NaHCO3(aq) + 2HCl(aq) ⇄ NaCl(aq) + H2O(l) + CO2(g): This reaction is a double displacement reaction and does not involve any transfer of protons. It is not a Brønsted-Lowry acid-base reaction.
d. AgNO3(aq) + NaCl(aq) ⇄ AgCl(s) + NaNO3(aq): This reaction is a double displacement reaction and does not involve any transfer of protons. It is not a Brønsted-Lowry acid-base reaction.
Therefore, the correct answer is b. NH4+(aq) + H2O(l) ⇄ NH3(aq) + H3O+(aq).