Question

Question one:

A mixture of salt (6 grams) plus water (10 grams) was made into saltwater. What is the final mass of the saltwater after all the salt dissolves?

Question two:
A student dissolves a 2-gram piece of Alka-Seltzer in 10 grams of water in a 12-gram test tube. As soon as the Alka-Seltzer reacts, the student puts a 0.5-gram balloon over the top of the test tube. The balloon filled with CO2. What is the final mass of the test tube/balloon after the reaction is complete?

Please answer quickly and correctly. Thank you! :)

Answer 1

1. 16 g

2. 24.5 g

Step-by-step explanation:

For question 1:

The mass of a solution is equal to the sum of the masses of the solute (the substance being dissolved, in this case, salt) and the solvent (the substance in which the solute is dissolved, in this case, water) when they are combined. Assuming that no mass is lost during the dissolving process, the mass of the saltwater solution would be the sum of the mass of the salt and the mass of the water.

So, the final mass of the saltwater would be:

`\text{Mass of saltwater $=$ Mass of salt $+$ Mass of water}\\ \\\\\\\Longrightarrow \text{Mass of saltwater} = 6 \ g + 10 \ g\\\\\\\\\therefore \boxed{\text{Mass of saltwater} = 16 \ g}`

Thus, the final mass of the saltwater is 16 grams.

For question 2:

The law of conservation of mass states that mass cannot be created or destroyed in a chemical reaction. Thus, the total mass of the reactants before the reaction will be the same as the total mass of the products after the reaction.

We are given:

• Mass of Alka-Seltzer: 2 grams

• Mass of water: 10 grams

• Mass of test tube: 12 grams

• Mass of balloon (before inflation): 0.5 grams

Thus, suming these values we get:

`\text{Total initial mass} = \text{Mass of Alka-Seltzer } + \text{ Mass of water } + \text{ Mass of test tube } + \text{ Mass of balloon}\\\\\\\\\Longrightarrow \text{Total initial mass} =2 \ g + 10 \ g + 12 \ g + 0.5 \ g\\\\\\\\\therefore \text{Total initial mass} =24.5 \ g`

When the Alka-Seltzer dissolves in water, it reacts to form CO₂ (among other products) which fills the balloon. The mass of the CO₂ was originally part of the mass of the Alka-Seltzer tablet, and so it remains part of the total mass after the reaction. Since the balloon is now filled with CO₂, its mass is still included in the total mass, but instead of being counted separately, it's now part of the combined system.

Therefore, even after the Alka-Seltzer reacts, the total mass of the test tube with the balloon on top will remain 24.5 grams, because no mass has left the system; it has only been redistributed from the Alka-Seltzer to the CO₂ gas within the balloon.