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

Observing color changes during reactions

Answer

Counting the number of molecules in reactions

Answer

Measuring temperature changes in reactions

Question 2

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

Accepted Answer

Excess reactant that did not get consumed in the reaction

Answer

Products that have decomposed

Answer

The limiting reagent

Answer

Molecules that were created during the reaction

Question 3

Which scenario correctly applies conservation of mass?

Accepted Answer

12 g reactant → 10 g product + 2 g gas

Answer

10 g reactant → 8 g product + 3 g gas

Answer

10 g reactant → 10 g product

Answer

15 g reactant → 14 g product

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

36.5 g

Answer

69 g

Answer

142 g

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

Mass is perfectly conserved in all nuclear reactions

Answer

Nuclear reactions create new mass

Answer

Conservation of mass does not apply to any reactions

Question 6

If 8 g of methane (CH₄) burns completely and produces 22 g of CO₂ and some water vapor, how much water vapor was produced?

Accepted Answer

18 g

Answer

9 g

Answer

14 g

Answer

36 g

Question 7

In a chemical reaction, 25 g of substance X and 15 g of substance Y react to produce substance Z and 5 g of a gas. What is the mass of Z?

Accepted Answer

35 g

Answer

15 g

Answer

25 g

Answer

45 g