counting atoms and conservation mass

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

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

A student heated a 10 gram sample of a chemical in an open container. A chemical reaction occurred, and the mass of the sample was measured again. The mass of the sample was found to be less than before the reaction. Which of the following best explains the decrease in mass of the sample?

• The heat caused the chemical to become less dense.

• The reaction gave off more heat than was added.

• Some of the lighter particles were destroyed.

• Some of the particles escaped as a gas formed.

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

Which of the models of a chemical reaction best represents the Law of Conservation of Mass?

• A

• B

• C

• D

Tags

NGSS.MS-PS1-5

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

Tags

NGSS.MS-PS1-5

NGSS.MS-PS1-2

Lynn had 100 mg of water and 50 mg of salt. She then combined the water and the salt and a chemical reaction occurred. What is the mass at the end of her experiment?

• 50

• 100

• 150

Tags

NGSS.MS-PS1-5

How many atoms of Oxygen are in Fe(NO₃)₃ ?

• 6
• 3
• 9
• 1

Tags

NGSS.MS-PS1-1

How many atoms of Iron in the following equation?

2HFe₅Cl

• 1

• 10

• 5

• 20

Tags

NGSS.MS-PS1-1

How many O's are in Al₂(SO₄)₃

• 4
• 12
• 7
• 24

Tags

NGSS.MS-PS1-1

Calculate the number of Oxygen atoms in Al(OH)₃

• 1

• 2

• 3

• 4

Tags

NGSS.MS-PS1-1

How many Sodium (Na) are in 6NaCl?

• 1
• 12
• 6