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Unformatted text preview: Version 072/ABACA – Quiz 4 – Lyon – (53385) 1 This print-out should have 6 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 1 2 3 4 5 6 7 AA AB AC AD BA BB BC 8 9 10 BACK NEXT BD CA CB CC CD 001 10.0 points A sample of an acid with an unknown con- centration was titrated with a known concen- tration of NaOH. However, before the NaOH was used in the titration, the NaOH was stan- dardized by titrating it with a solution con- taining a known mass of pure KHP. The rea- son the NaOH had to be standardized with the pure KHP is because the NaOH pellets used to make the NaOH solution were prob- ably impure and would be difficult to weigh accurately. 1. False 2. True correct Explanation: Most inorganic bases are solid metal hy- droxides, which react readily with CO 2 in the atmosphere and absorb water from the air. These properties make solid NaOH pellets impure and difficult to weigh out accurately. Primary standards, such as pure KHP, are used to standardize NaOH solutions in order to establish an accurate NaOH molarity for an acid-base titration. The reason that pri- mary standards, such as KHP, are not used to titrate unknown concentrations of acids or bases is because of cost. Pure primary standards are very expensive and many are difficult to prepare; therefore, they are used...
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This note was uploaded on 10/21/2009 for the course CH 53395 taught by Professor Lyon during the Spring '09 term at University of Texas.
- Spring '09