Equations

Question 1

Define reactants.

Answer 1

In a chemical reaction, the substances that undergo a chemical change in a reaction.

Question 2

What are chemical equations used for?

Answer 2

To model the changes that happen in chemical reactions.

Question 3

Define products.

Answer 3

In a chemical reaction, the new substances formed.

Question 4

How do you balance an equation?

Answer 4

Count the symbols on both sides of the equation.

You may need to put a number like 2 (normal size) in front of one of the symbols to make the numbers equal.

Question 5

What are the state symbols?

Answer 5

State symbols show the physical state of each substance in a balanced equation.

• solid(s)
• gas(g)
• liquid(l)
• aqueous solution [something dissolved in water] (aq)

Question 6

Balance this equation:
Fe[2]O[3] + C -> Fe + CO

Element: Fe | O | C
On Left: 2 | 3 | 1
On Right: 1 | 1 | 1

Answer 6

Fe[2]O[3] + 3C -> 2Fe + 3CO

Element: Fe | O | C
On Left: 2 | 3 | 3
On Right: 2 | 3 | 3

Question 7

Balance these chemical equations:

• Mg + 0[2] -> MgO
• N[2] + H[2] -> NH[3]
• CH[4] + O[2] -> CO[2] +H[2]O

Answer 7

• 2Mg + O[2] -> 2MgO
• N[2] + 3H[2] -> 2NH[3]
• CH[4] + 2O[2] -> CO[2] + 2H[2]O

Question 8

Aluminium reacts with hot dilute sulfuric acid, H[2]SO[4].
Aluminium sulfate, Al2[3] and hyrdogen, H[2], are formed.
Write a balanced equation for this reaction and include state symbols

Answer 8

Unbalanced equation:
Al + H[2]SO[4] -> Al2[3] + H[2]

-There are 2 Al atoms on the right, so a 2 is placed in front of the Al on the left.
2Al2[3]
-There are 3 units of SO[4] on the right, so a 3 is placed in front of the H[2]SO[4] on the left.
3H[2]SO[4]
-There are now 3 x H[2] on the left, so a 3 is placed in front of the H[2] on the right.
3H[2]

With the state symbols:

2Al(s) + 3H[2]SO4 -> Al23 + 3H2

Question 9

Balance these chemical equations and include state symbols:
* CuO + HNO[3] -> Cu(NO[3])[2] + H[2]O
(the reaction between copper oxide powder and dilute nitric acid, forming copper nitrate solution and water)
* Fe + Cl[2] -> FeCl[3]
(the reaction between iron filings and chlorine gas, forming iron chloride powder)

Answer 9

• CuO(s) + 2HNO3 -> Cu(NO[3])2 + H[2]O

* 2Fe(s) + 3Cl2 -> 2FeCl3