Question

kc: conservation of mass quiz prep
name: __ pg #. __

1. in a reaction of 22.99 g of sodium with 35.45 g of chlorine, what mass of sodium chloride is formed? write a chemical word equation and then solve the problem.

1. a 12.2 g sample of x reacts with a sample of y to form 78.9 g of xy. what is the mass of y that reacted? write a chemical word equation and then solve the problem.

1. you are going to mix solutions of potassium iodide and lead nitrate. you record the mass of both solutions, and then mix them together and mass the resulting yellow precipitate that is formed. will the mass change during this experiment? why or why not? use the word \particles\ in your explanation.

1. there will be questions about mass, volume, and the law of conservation of mass. study those definitions in your notes now.

Explanation:

Question 1

Step 1: Write the word equation

Sodium + Chlorine → Sodium Chloride

Step 2: Apply the law of conservation of mass

The law of conservation of mass states that the total mass of reactants equals the total mass of products. So, mass of sodium + mass of chlorine = mass of sodium chloride.

Step 3: Calculate the mass of sodium chloride

Mass of sodium = 22.99 g, Mass of chlorine = 35.45 g.
Mass of sodium chloride = 22.99 g + 35.45 g = 58.44 g

Step 1: Write the word equation

X + Y → XY

Step 2: Apply the law of conservation of mass

Mass of X + Mass of Y = Mass of XY. So, Mass of Y = Mass of XY - Mass of X.

Step 3: Calculate the mass of Y

Mass of X = 12.2 g, Mass of XY = 78.9 g.
Mass of Y = 78.9 g - 12.2 g = 66.7 g

According to the law of conservation of mass, in a chemical reaction, the total number of particles (atoms, ions, molecules) of reactants remains conserved as they rearrange to form products. When potassium iodide and lead nitrate solutions are mixed, a chemical reaction occurs (Potassium Iodide + Lead Nitrate → Lead Iodide (yellow precipitate) + Potassium Nitrate). The total mass of the reactants (potassium iodide solution + lead nitrate solution) should equal the total mass of the products (lead iodide precipitate + potassium nitrate solution). However, if we only measure the mass of the yellow precipitate (lead iodide) and compare it to the mass of the two solutions, we might think there's a change, but actually, the mass of the precipitate plus the mass of the remaining solution (potassium nitrate solution) equals the initial mass of the two reactant solutions. Since we are only measuring the precipitate, but the total mass of all particles (in precipitate and remaining solution) is conserved. So, the total mass of all substances involved (particles) before and after the reaction remains the same, so the overall mass (if we consider all products and reactants) does not change. If we only consider the precipitate vs. the two solutions, the measured mass of the precipitate alone is less than the mass of the two solutions, but that's because we aren't measuring the entire product (the remaining solution is also a product). But strictly, the total mass of particles (all reactant particles become product particles) is conserved.

Answer:

The mass of sodium chloride formed is 58.44 g. The word equation is Sodium + Chlorine → Sodium Chloride.

Question 2