Ch 11 - Connecting chemical reactions and equations

Question 1

What are the rules for balancing chemical equations?

Answer 1

1. Write the reactants and products using the correct formula and state for each substance.
2. Count the number of atoms of each element on the left-hand side of the equation. Do the same for the right-hand side and compare for each element. If any of these numbers do not match, the equation is not balanced and you need to proceed to the following steps.
3. Balance by placing coe cients in front of the formulas. Do not change the actual formula. If any substance is present as an element, leave the balancing of it to last.
4. Check all atoms or ions to ensure that they are balanced.
5. Make sure that the coe cients are in their lowest possible ratio.

Question 2

What observations could suggest to us that chemical changes are taking place.

Answer 2

1. A substance disappears.
2. A gas is given off. ( ie production of a gas as a result of a chemical change is called effervescence.)
3. A solid is precipitated. (Precipitation is the formation of a new substance that is only slightly soluble and settles as a solid.)
4. A colour change takes place.
5. Thee temperature changes.
6. A new odour is released.
7. Light is given out.