Chemical Reactions FA#5

Energy cannot be created or destroyed, it just changes form. This principle is known as what?

• Conservation of matter

• endothermic reaction

Answer explanation

remember, energy cannot just disappear! It must go somewhere or transfer into different forms

The atomic number of an element is also known as what?

• # of protons

• # of electrons

• #of neutrons

• mass number

Answer explanation

this is always above an elements name

For any neutral atom on the periodic table, the # of protons are equal to what?

• # of electrons

• #of neutrons

• atomic weight

• # of compounds

Answer explanation

Protons and electrons will always be the same for any neutral atom!

How many iron atoms are in the compound?

Answer explanation

there are 4 Fe (iron atoms).....2 on the outside is the coefficient and the 2 is the subscript for Fe

How many total carbon dioxide compounds are present?

Answer explanation

There are 5 total carbon dioxide compounds since there is a 5 coefficient in front

How many total oxygen atoms are present?

Answer explanation

10

The 5 indicates how many total carbon dioxide compounds and since there are 2 oxygens (as indicated by the subscript), you have to multiply the 5 times 2.

Carbon has an atomic # of 6. How many protons does carbon have?

Answer explanation

6, since the atomic # is the same # of protons in an atom

Carbon has an atomic weight of 12.011 and an atomic # of 6. How many neutrons does carbon have?

Answer explanation

6 neutrons (12-6= 6)

As represented on the periodic table, iron can be written as Fe. What does “Fe” also represent (besides the name for iron)

Answer explanation

Element symbol

All elements on the periodic table have a name and element symbol

200 grams of ice are placed in a sealed cup and start to melt. 200 grams of liquid water were measured after the ice melted. Explain why the system had to be “closed” in order to have the exact measurements of ice/liquid

Answer explanation

Conservation of matter explains that matter cannot be created or destroyed, it just changes form in a closed system. The system must be closed so that extra air doesn’t get in or escape