RPAL Conservation of Mass 3

Question 1

Antoine Lavoisier established the law of conservation of mass in the 18th century primarily by:

Accepted Answer

Carefully measuring masses before and after reactions in sealed containers

Answer

Lavoisier used precise mass measurements in sealed containers to show that total mass is unchanged before and after chemical reactions.

Question 2

In the PhET RPAL simulation, the 'leftovers' represent:

Accepted Answer

Excess reactant that did not get consumed in the reaction

Answer

Leftovers in RPAL are the excess reactant molecules remaining after the limiting reagent is fully consumed.

Question 3

Which scenario correctly applies conservation of mass?

Accepted Answer

12 g reactant → 10 g product + 2 g gas

Answer

12 g reactant producing 10 g product + 2 g gas satisfies conservation of mass because 10 + 2 = 12 g total product mass.

Question 4

A reaction between hydrogen and chlorine produces HCl. If 2 g of H₂ reacts with 71 g of Cl₂, what mass of HCl is produced?

Accepted Answer

73 g

Answer

By conservation of mass, 2 g H₂ + 71 g Cl₂ = 73 g HCl.

Question 5

Which statement about conservation of mass in nuclear reactions is correct?

Accepted Answer

A small amount of mass converts to energy in nuclear reactions, so mass alone is not conserved

Answer

In nuclear reactions, mass-energy equivalence (E=mc²) means a tiny amount of mass converts to energy, so conservation of mass applies to chemical but not nuclear reactions.

RPAL - Reactants, Products, and Leftovers Practice Test

RPAL - Reactants, Products, and Leftovers Practice Test

RPAL Conservation of Mass 3