Chemical Reactions

When elements react, their atoms join with other atoms to form compounds. This involves giving, taking or sharing and the atoms are held together by chemical .

We can write down a reaction in two forms, a word equation or a chemical symbol equation. The chemicals that are put into the reaction are called reactants, and those that are made are called products. They are separated by an arrow which is read as 'goes to'

Reactants → Products

No atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants. This is known as 'Conservation of Mass'. This is often forgotten when one of the reactants or products is a gas, as it can not be weighted.

1. When 24 grams of magnesium reacted with 16 grams of oxygen magnesium oxide was formed. What is the mass of magnesium oxide was made?
   grams
2. Some carbon was reacted with 4 grams of hydrogen to make 16 grams of methane. How much of carbon was used?
   grams
3. 10 grams of potassium nitrate solution was mixed with 15 grams of sodium iodide solution to make a solid yellow precipitate in 20 grams of a sodium nitrate solution. What is the mass of the solid yellow precipitate?
   grams
4. It was found that 39.8 grams of copper (II) sulfide was formed when 31.8 grams of copper reacted with sulfur. How much sulfur was used?
   grams
5. How many grams of sodium are needed to combine with 35.5 grams of chlorine to make 58.5 grams of sodium chloride?
   grams
6. When 40.3 grams of magnesium oxide is placed in 73 grams of hydrochloric acid, 95.3 grams of magnesium chloride form along with some water. What mass of water forms?
   grams
7. When 72 grams of water is decomposed, 8 grams of hydrogen is made along with some oxygen. What mass of oxygen is made?
   grams
8. How many grams of hydrogen gas are formed after 24.3 grams of magnesium metal are added to 73 grams of hydrochloric acid making 95.3 grams of magnesium chloride and the hydrogen gas?
   grams
9. How many grams of magnesium oxide are formed when 2.4 grams of magnesium are combined with 1.6 grams of oxygen?
   grams
10. How many grams of methane need to be combined with 64 grams of oxygen to make 44 grams of carbon dioxide and 36 grams of water?
    grams