Unit Test — Unit test Answers

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21
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Which pure substance can be classified as an element?

A
H2
B
NO3
C
NaCl
D
H2SO4
22
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Which element is classified as an alkali metal?

A
Rb
B
Sr
C
Zr
D
Cl
23

Which physical method can be used for obtaining a sample of salt from a small beaker of salt water?

A
boiling
B
freezing
C
chromatography
D
sorting
24

How did Niels Bohr describe electrons in his atomic model?

A
Their energies can have any values.
B
Their exact positions cannot be known.
C
They have high probability to be found in certain regions.
D
They orbit the central nucleus in discrete paths.
25

Which element is the most reactive?

A
sodium
B
nickel
C
carbon
D
oxygen

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