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General Chemistry Principles, Patterns, and Applications, 2011

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7. ♦ Sodamide, or sodium amide, is prepared from sodium metal <strong>and</strong> gaseous ammonia. Sodamide contains the<br />

amide ion (NH 2 − ), which reacts with water to form the hydroxide anion by removing an H + ion from water.<br />

Sodium amide is also used to prepare sodium cyanide.<br />

a. Write the formula for each of these sodium-containing compounds.<br />

b. What are the products of the reaction of sodamide with water?<br />

8. A mixture of isooctane, n-pentane, <strong>and</strong> n-heptane is known to have an octane rating of 87. Use the data<br />

in Figure 2.25 "The Octane Ratings of Some Hydrocarbons <strong>and</strong> Common Additives" to calculate how much<br />

isooctane <strong>and</strong> n-heptane are present if the mixture is known to contain 30% n-pentane.<br />

9. A crude petroleum distillate consists of 60% n-pentane, 25% methanol, <strong>and</strong> the remainder n-hexane by mass<br />

(Figure 2.25 "The Octane Ratings of Some Hydrocarbons <strong>and</strong> Common Additives").<br />

a. What is the octane rating?<br />

b. How much MTBE would have to be added to increase the octane rating to 93?<br />

10. Premium gasoline sold in much of the central United States has an octane rating of 93 <strong>and</strong> contains 10%<br />

ethanol. What is the octane rating of the gasoline fraction before ethanol is added? (See Figure 2.25 "The<br />

Octane Ratings of Some Hydrocarbons <strong>and</strong> Common Additives".)<br />

A N S W E R S<br />

1.<br />

3. MgO, magnesium oxide<br />

5. Carbonic acid is H 2 CO 3 ; lithium carbonate is Li 2 CO 3.<br />

7.<br />

a. Sodamide is NaNH 2 , <strong>and</strong> sodium cyanide is NaCN.<br />

b. Sodium hydroxide (NaOH) <strong>and</strong> ammonia (NH 3 ).<br />

9.<br />

a. 68<br />

b. 52 g of MTBE must be added to 48 g of the crude distillate.<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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