Chemistry Retest Practice

How many different elements are represented in the compound Na₂CO₃?

• 1
• 2
• 3
• 4

Tags

NGSS.MS-PS1-1

Italian salad dressing is a

• heterogeneous mixture
• homogeneous mixture
• pure Substance
• compound

This appears on the left side of a chemical formula, and represents how many molecules there are. 

• An Atom
• The Subscript
• A Molecule
• The Coefficient

How many hydrogen atoms are in this chemical formula: 2H₂O?

• 4 hydrogen atoms
• 1 hydrogen atom
• 2 hydrogen atoms
• 3 hydrogen atoms

Tags

NGSS.MS-PS1-1

How many oxygen atoms are in this chemical formula: H₃PO₄?

• 7 oxygen atoms
• 4 oxygen atoms
• 3 oxygen atoms
• 1 oxygen atoms

How many Magnesium atoms are in 3MgCl₂?

• 3
• 5
• 1
• 6

Tags

NGSS.MS-PS1-1

The law of conservation of mass states that 

• matter is created
• matter is destroyed
• matter is neither created nor destroyed
• matter does not change

Tags

NGSS.MS-PS1-5

Is this equation balanced?

• Yes
• No
• Not enough information

What is the law of conservation of mass?

• Matter changes when reacted or changed.
• The mass of all reactants are changed during a physical or chemical change
• The mass of the reactants is the same as the mass of the products
• The mass of the products is different than the mass of the reactants.

Suppose a reaction were to happen in an open container in a lab. During the reaction, the scientist observes the chemicals bubble and produce a gas. During the analysis the scientist notices that the reactants weighed 20 g when he started, and the product weighed 18 g. Explain what happened.  

• His chemical reaction defied the law of conservation of mass
• The product destroyed mass during the reaction
• The reactants created matter during the reaction
• The gas that was produced was not able to be weighed since the container was open.