Question

1. the illustration to the right shows a conservation of mass experiment. why did the solution in the beaker lose mass?

a. materials have less mass at high temperatures
b. the mass of the reactants and products was less than 100 g
c. sodium sulfate is lighter than air
d. some of the water molecules turned into gas and escaped the beaker

1. explain why the model of this chemical reaction obeys the law of conservation of matter

a. because there are the same number of atoms of each element shown on both sides
b. because they both start and end with diatomic (two - atomed) molecules
c. because they both start and end with the same types of particles
d. because they both start and end with two sets of particles
image and chemical equation: h₂so₄ + 2naoh → na₂so₄ + 2h₂o, with initial (after h₂so₄ is completely added) and final (after exothermic reaction is completed) setups, initial mass 100 g, final mass 100 g but with heat and gas - like symbols

Explanation:

Question 75

To determine why the solution in the beaker loses mass, we analyze each option:

• Option A: Mass is not lost due to materials having less mass at high temperatures. Mass conservation is about matter, not temperature - related mass change.
• Option B: The law of conservation of mass states mass of reactants equals products. So this is incorrect.
• Option C: Sodium sulfate's density relative to air doesn't cause mass loss from the beaker (the beaker contains liquid solution, not related to air's density for mass loss here).
• Option D: The reaction is exothermic (releases heat), which can cause water molecules to turn into gas (vapor) that escapes the beaker, leading to a decrease in the solution's mass.

The Law of Conservation of Matter (Mass) states that in a chemical reaction, the total number of atoms of each element remains the same before and after the reaction (atoms are rearranged, not created or destroyed).

• Option A: The model shows that for each element (Na, H, S, O), the number of atoms on the reactant side (in \(H_2SO_4\) and \(2NaOH\)) and product side (in \(Na_2SO_4\) and \(2H_2O\)) is conserved. For example, Na: 2 on reactant (2NaOH) and 2 on product (\(Na_2SO_4\)); H: 4 on reactant (\(H_2SO_4\) has 2, 2NaOH has 2) and 4 on product (2\(H_2O\)); S: 1 on reactant and 1 on product; O: 8 on reactant (\(H_2SO_4\) has 4, 2NaOH has 2 each, total 4 + 4 = 8) and 8 on product (\(Na_2SO_4\) has 4, 2\(H_2O\) has 2 each, total 4+4 = 8). So the same number of atoms of each element is present on both sides.
• Option B: The molecules are not all diatomic. Reactants are \(H_2SO_4\) (polyatomic) and \(NaOH\) (polyatomic ions in solution), products are \(Na_2SO_4\) (polyatomic ion) and \(H_2O\) (diatomic? No, \(H_2O\) is triatomic). So this is incorrect.
• Option C: The particles (atoms, ions, molecules) change types (reactants are \(H_2SO_4\) and \(NaOH\) particles, products are \(Na_2SO_4\) and \(H_2O\) particles), so they are not the same types. Incorrect.
• Option D: The "two sets of particles" reasoning is not related to the Law of Conservation of Matter. The law is about atom conservation, not sets of particles. Incorrect.

Answer:

D. Some of the water molecules turned into gas and escaped the beaker

Question 76