Law of conservation of Mass

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products
• a total of 10g of products
• a total of 80 g of products
• a total of 20g of products

The coefficient in  3H₂O is

• 6
• 2
• 3
• 5

In a reaction A + B ----> C,  reactant A has 5g and product  C has 9g. How many grams does reactant B should have? 

• 4g
• 5g
• 9g
• 14g

How many nitrogen atoms does NH₃ have?

• 1
• 2
• 3
• 4

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit
• Invisible
• Transformed, changed
• None of the above

This type of system allows matter to flow freely in and out...

• Closed System
• Open System

12g of Carbon react with 16g of Oxygen, how much carbon monoxide (CO) is formed? 

• 28 g
• 4g
• 30g
• 12g

The number to the lower side of an element is a 

• Subscript
• Superscript
• Coefficient
• Charge

The coefficient in  3H₂O is

• 6
• 2
• 3
• 5

What will weigh more when a chemical change is complete?  The reactants before the chemical reaction, or the product after the reaction is complete?

• They both will weigh the same
• The product always weighs more than the reactant
• The reactant will weigh more than the product
• They both will loose mass after the reaction