1. i will be able to repair your laptop tomorrow. 2. he was able to answer the question correctly. 3. i will able to come with you. 4. my little sister is able to count to 100. 5. i was able to speak to tom before he left. 6. i will be able to translate this document without your help. 7. she will be able to have luch with you. 8. they were able to finish the work. 9. we were not able to buy tickets, so we did not go to the concert. 10. we will not able to solve this problem by ourselves.
it has already been explained that an ester is the product formed by the reversible reaction between an acid and alcohol. if an acid and an alcohol are mixed, a condition of equilibrium will eventually be set up when the rates of the direct reaction (etherification) and the reverse reaction (hydrolysis) are equal. it follows from the law of mass action that an increase in the molecular concentration of anyone of the reacting substances will displace the equilibrium in the opposite direction. any excess of water will diminish the proportion of ester present at equilibrium. consequently, in the preparation of esters, it is necessary as a rule to use the anhydrous acid and alcohol in order to obtain good yields, and the reaction is usually carried out in the presence of an acid catalyst (concentrated sulfuric acid or dry hydrogen chloride). an ester may be almost completely hydrolyzed if it is heated with water, provided that a large enough proportion of water is used. the hydrolysis is usually slow, but is catalyzed by acids. it becomes complete if a dilute solution of an alkali is used instead of water, for the acid produced by hydrolysis is neutralized by the alkali as fast as it is formed, and so can take no further part in the reaction. most esters of organic acids are pleasant-smelling, volatile liquids and many of them are used in perfumery and in the production of artificial flavoring agents. ethyl acetate is a typical example of an ester of an organic acid. it is formed when acetyl chloride or acetic anhydride acts on ethyl alcohol. ethyl acetate is prepared by the interaction of alcohol and glacial acid, in the presence of concentrated sulfuric acid.
