Man's physical universe

xanabras

I

566 MAN IS MASTERING HIS MATERIAL WORLD

wheat for protein, for example, and the baker usually checks this

analysis to make sure that he receives what he has paid for. A carload

of iron, copper, silver, or some other ore is paid for on the basis of

analysis. A small change in the decimal place of the atomic weight of

an element might make a difference of thousands of dollars in the

amount paid to a large mine each year, for all calculations based on

analyses employ atomic weights. It is exceedingly important, therefore,

that atomic weights be known as accurately as human ingenuity

will permit.

1. Define atom and molecule.

STUDY QUESTIONS

2. State the main points of Dalton's atomic theory.

3. State the law of conservation of mass.

4. What does Dalton's atomic theory explain?

5. State Avogadro's number. What does it mean?

6. What do chemical equations represent? Of what value are chemical equations?

7. What is (1) a molecular weight, (2) a gram-molecular weight?

8. What is a combining weight of an element?

9. What is the relation between the combining weight of an element and its

atomic weight?

10. What is valence? What information is required in order to obtain the valence

of an element in a given compound?

IL State the law of definite composition.

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