The oxidation state of selenium in NaSeO₃ is

• +5

• +3

• +7

• -5

In the reaction 2Ca(s) + O₂(g) --> 2CaO(s), calcium is __________

• reduced

• oxidized

• electrolyzed

• synthesized

Tags

NGSS.HS-PS1-2

In the reaction N₂(g) + 3 H₂(g) --> 2 NH₃(g), nitrogen is __________.

• reduced

• oxidized

• electrolyzed

• synthesized

Tags

NGSS.HS-PS1-2

Oxygen usually has an oxidation number of ___ when it is combined with other elements in a compound.

• +6

• -6

• +2

• -2

Hydrogen usually has an oxidation number of ___ when it is combined with other elements in a compound.

• -1

• +2

• +1

• -2

Elements not combined with other elements in a compound have an oxidation number of ____.

• Depends on their group on the periodic table

• +1

• 0

• = to the number of valence elections

The emission of which particle does NOT cause the formation of a new element?

• Gamma

• Alpha

• Positron

• Beta

Tags

NGSS.HS-PS1-8

When thorium-234 emits a beta particle the new nucleus has a mass number of _____.

• 233

• 235

• 234

• You cannot determine the answer from the information provided.

Tags

NGSS.HS-PS1-8

The half life period of a radioactive element is 20.0 weeks. After 80.0 weeks what mass would be left if the original size of the sample was 240 grams?

• 15 grams

• 0 grams

• 7.5 grams

• 60 grams

The energy released in an atomic bomb explosion is mainly due to .....

• a lower mass of products than the initial material.

• a greater mass of products than the initial material.

• the release of electrons.

• the release of neutrons.

Tags

NGSS.HS-PS1-8