Вопрос
10. Determine the concentration of NaCl in the solution (g/1) , if the following results were obtained during potentiometri titration of 20.0 ml of a solution of 0.2000 M AgNO_(3) 11. Determine the concentration of cadmium in the solution if D=0.7210^-5cm^2s^-1,m=2.0 mg/s,tau =4.4 s, and the current strength is 10mu A 12. The molar absorption coefficien t of silver in a complex with dithizone in solution at 462 nm is 30500 . Calculate the minimum concentration in mol/1 of the complex of silver with dithizone, which can be determined by the photometric method at an absorbing layer thickness of 1=1 cm, if the minimum optical density recorded by the device is equals 0.01
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10. To determine the concentration of NaCl in the solution, we can use the concept of stoichiometry and the given information about the titration of AgNO3.<br /><br />Given:<br />- Volume of NaCl solution: 20.0 mL<br />- Concentration of AgNO3 solution: 0.2000 M<br /><br />The balanced chemical equation for the reaction between NaCl and AgNO3 is:<br />NaCl + AgNO3 → NaNO3 + AgCl<br /><br />From the balanced equation, we can see that 1 mole of NaCl reacts with 1 mole of AgNO3.<br /><br />To find the concentration of NaCl, we need to calculate the number of moles of AgNO3 used in the titration.<br /><br />Number of moles of AgNO3 = Concentration of AgNO3 × Volume of AgNO3 solution<br />Number of moles of AgNO3 = 0.2000 M × (20.0 mL / 1000 mL/L)<br />Number of moles of AgNO3 = 0.004 mol<br /><br />Since the reaction is 1:1, the number of moles of NaCl will be the same as the number of moles of AgNO3.<br /><br />Now, we can calculate the concentration of NaCl using the formula:<br /><br />Concentration of NaCl = Number of moles of NaCl / VolumeCl solution<br />Concentration of NaCl = 0.004 mol / (20.0 mL / 1000 mL/L)<br />Concentration of NaCl = 0.2000 M<br /><br />Therefore, the concentration of NaCl in the solution is 0.2000 M.<br /><br />11. To determine the concentration of cadmium in the solution, we can use the given values and the formula for the relationship between current, charge, and concentration.<br /><br />Given:<br />- Diffusion coefficient (D) = 0.7210^-5 cm^2/s<br />- Mass flow rate (m) = 2.0 mg/s<br />- Time (τ) = 4.4 s<br />- Current strength (I) = 10 μA<br /><br />The relationship between current, charge, and concentration is given by the formula:<br /><br />I = (m / (z × F)) × (1 / (D × τ))<br /><br />Where:<br />- I is the current strength<br />- m is the mass flow rate<br />- z is the charge of the cadmium ion (2 for Cd^2+)<br />- F is the Faraday constant (96485 C/mol)<br />- D is the diffusion coefficient<br />- τ is the time<br /><br />Rearranging the formula to solve for the concentration:<br /><br />Concentration = (m × D × τ) / (I × z × F)<br /><br />Substituting the given values:<br /><br />Concentration = (2.0 mg/s × 0.7210^-5 cm^2/s × 4.4 s) / (10 μA × 2 × 96485 C/mol)<br />Concentration = 1.57 × 10^-6 mol/L<br /><br />Therefore, the concentration of cadmium in the solution is 1.57 × 10^-6 mol/L.<br /><br />12. To calculate the minimum concentration of the complex of silver with dithizone, we can use the Beer-Lambert law.<br /><br />Given:<br />- Molar absorption coefficient (ε) = 30500 L/mol·cm<br />- Absorbing layer thickness (l) = 1 cm<br />- Minimum optical density (A) = 0.01<br /><br />The Beer-Lambert law states that the optical density (A) is directly proportional to the concentration (c) of the absorbing species:<br /><br />A = ε × c × l<br /><br />Rearranging the formula to solve for the concentration:<br /><br />c = A / (ε × l)<br /><br />Substituting the given values:<br /><br />c = 0.01 / (30500 L/mol·cm × 1 cm)<br />c = 3.28 × 10^-7 mol/L<br /><br />Therefore, the minimum concentration of the complex of silver with dithizone that can be determined by the photometric method is 3.28 × 10^-7 mol/L.
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