015 10 points what is the ph of an acid solution

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015 1.0 points What is the pH of an acid solution obtained by mixing 200 mL of 0.0155 M H 2 SO 4 and 300 mL of an 0.210 M HCl solution? Assume all of the acids dissociate. 1. 0.460 2. 0.523 3. 1.2 4. 0.859 correct 5. 2.2 6. 1.16 7. 1.9 Explanation: V H 2 SO 4 = 200 mL [H 2 SO 4 ] = 0.0155 M V HCl = 300 mL [HCl] = 0.210 M To determine the pH of the final mixture, we need to determine how many moles H + is being contributed by each acid. ? mol H + = 0 . 200 L × 0 . 0155 mol H 2 SO 4 1 L × 2 mol H + 1 mol H 2 SO 4 = 0 . 0062 mol H + ? mol H + = 0 . 300 L × 0 . 210 mol HCl 1 L × 1 mol H + 1 mol HCl = 0 . 063 mol H + Add these two quantities together and divide by the total volume to get [H + ]. [H + ] = 0 . 063 mol + 0 . 0062 mol 0 . 2 L + 0 . 3 L = 0 . 138 M H + pH = - log[0 . 138] = 0 . 859 016 1.0 points What is the [H 3 O + ] in a 0 . 050 M solution of Ba(OH) 2 ? 1. 1 . 0 × 10 13 M correct 2. 2 . 0 × 10 13 M 3. 2 . 0 × 10 5 M 4. 5 . 0 × 10 2 M 5. 5 . 0 × 10 10 M 6. 1 . 0 × 10 5 M Explanation: [Ba(OH) 2 ] = 0 . 050 M Ba(OH) 2 is a strong base and completely ionizes in aqueous solution. Ba(OH) 2 Ba 2+ + 2 OH ini, M 0.05 0 0 Δ, M - 0 . 05 +0 . 05 +2(0 . 05) fin, M 0 0 . 05 0 . 10 [OH ] = 0 . 10 = 1 . 0 × 10 1 M K w = [H 3 O + ][OH ] = 1 × 10 14 [H 3 O + ] = K w [OH ] = 1 . 0 × 10 14 1 . 0 × 10 1 = 1 . 0 × 10 13 M 017 1.0 points Consider the statements Z1) A 0.05 M HCl solution has the same pH as 0.05 M HCN. Z2) A 0.10 M solution of a weak acid has the same pH as a 0.10 M solution of a weak base that has the same ionization constant. Z3) A solution in which pH equals pOH must be neutral.
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tu (pyt67) – Homework 4 – Fakhreddine – (52425) 5 Z4) An acidic solution contains H 3 O + but no OH , while a basic solution contains OH but no H 3 O + . Which response includes all the above statements that are true? 1. Z3 only correct 2. Z1 and Z3 only 3. None of these is correct. 4. Z2 and Z4 only 5. Z1 and Z4 only Explanation: HCl is a strong acid which completely disso- ciates in aqueous solution but HCN is a weak acid which only partially ionizes in solution. So 0.05 M HCl contains more H 3 O + than 0.05 M HCN. If K a for a weak acid has the same numeri- cal value as K b for a weak base, [H 3 O + ] of the acid equals [OH ] of the base. In acidic solutions [H 3 O + ] > [OH ]; in ba- sic solutions [H 3 O + ] < [OH ]; in neutral so- lutions [H 3 O + ]=[OH ] 018 1.0 points For a given weak acid HA the value of K a 1. cannot be greater than 10 7 . 2. changes with the pH of the solution. 3. does not change with temperature. 4. None of these correct 5. changes if we add a strong acid to a solution of the weak acid. 6. changes if we add a strong base to a solution of the weak acid. 7. cannot be less than 10 7 . Explanation: 019 1.0 points A 0.200 M solution of a weak monoprotic acid HA is found to have a pH of 3.00 at room temperature. What is the ionization constant of this acid? 1. 5.0 × 10 3 2. 5.30 3. 2.0 × 10 5 4. 2.0 × 10 9 5. 1.0 × 10 6 6. 1.8 × 10 5 7. 5.0 × 10 6 correct 8. 1.0 × 10 3 Explanation: 020 1.0 points We make a 1.0 M solution of an unknown acid HX. With a pH meter, we determine that the pH of the solution is 4.00. Which of
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  • Fall '07
  • Holcombe
  • pH, Acids

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