Rubbing alcohol is a 90 mass % solution of isopropyl alcohol, C3H8O, in water.

How many grams of rubbing alcohol contains 20.0 g of isopropyl alcohol?

100 g soln x (20/90) = ??

To determine how many grams of rubbing alcohol contains 20.0 g of isopropyl alcohol, we need to calculate the total mass of rubbing alcohol.

Given:
Mass of isopropyl alcohol (C3H8O) = 20.0 g
Mass % of isopropyl alcohol in rubbing alcohol = 90%

Step 1: Calculate the total mass of rubbing alcohol
Let's assume the total mass of rubbing alcohol is "x" grams.

Since the mass % of isopropyl alcohol in rubbing alcohol is 90%, it means that in 100 grams of rubbing alcohol, 90 grams is isopropyl alcohol.

Therefore, we can set up the following equation:
20.0 g / x g = 90% / 100%

Step 2: Solve for x
To solve for x, we can use cross-multiplication.

20.0 g * 100% = x g * 90%
2000 g = 90x

Step 3: Calculate the value of x
To find the value of x, divide both sides of the equation by 90.

x = 2000 g / 90
x ≈ 22.22 g

Therefore, approximately 22.22 grams of rubbing alcohol contain 20.0 grams of isopropyl alcohol.

To find the grams of rubbing alcohol that contains 20.0 g of isopropyl alcohol, we need to consider that rubbing alcohol is a 90 mass % solution of isopropyl alcohol in water.

Step 1: Calculate the total mass of rubbing alcohol.
Rubbing alcohol is a mixture of isopropyl alcohol and water. Since the total mass of the solution is 100%, we can assume that the remaining 10% is water.

Given that we have 20.0 g of isopropyl alcohol, we can calculate the total mass of the rubbing alcohol using the formula:

Total mass = Mass of isopropyl alcohol / Solution mass fraction

Since rubbing alcohol is a 90 mass % solution, the solution mass fraction is 0.90. Thus:

Total mass = 20.0 g / 0.90
Total mass = 22.2222... g (rounded to 4 decimal places)

Step 2: Subtract the mass of isopropyl alcohol from the total mass of the rubbing alcohol to find the mass of water.

Mass of water = Total mass - Mass of isopropyl alcohol
Mass of water = 22.2222... g - 20.0 g
Mass of water = 2.2222... g (rounded to 4 decimal places)

Therefore, 20.0 g of isopropyl alcohol corresponds to approximately 22.2222 g of rubbing alcohol, which contains approximately 2.2222 g of water.