Lyle stirs 5.0 grams of salt into a beaker of water. He then adds 15.0 grams of pure iodine to the mixture. If the total mass of the new mixture is 225 grams, what is the mass of the water?

Question

A.
100 grams
B.
205 grams
C.
200 grams
D.
20 grams

Answer 1

To find the mass of the water, we can use the information given about the total mass of the new mixture.

We know:

• Mass of salt = 5.0 grams
• Mass of iodine = 15.0 grams
• Total mass of the mixture = 225 grams

Let $m$ be the mass of the water. The equation for the total mass of the mixture can be expressed as:

$$m+\text{mass of salt}+\text{mass of iodine}=\text{total mass}$$

Substituting the values we have:

$$m+5.0,\text{grams}+15.0,\text{grams}=225,\text{grams}$$

Combining the known masses:

$$m+20.0,\text{grams}=225,\text{grams}$$

To find $m$, subtract 20.0 grams from both sides:

$$m=225,\text{grams}-20.0,\text{grams}$$ $$m=205,\text{grams}$$

Therefore, the mass of the water is 205 grams, which corresponds to option B.