Question

How many cups do you need for 4 moles rock salt (NaCl)? Rock salt weighs 520g per 1 cup

How many cups do you need for 1 kg of ice? Ice cubes weigh 220g per 1 cup

Answer 1

(1) The number of cups needed are, 0.45 cups.

(2) The number of cups needed are, 5 cups.

Explanation :

Part 1:

First we have to calculate the moles of NaCl.

`\text{Moles of NaCl}=\frac{\text{Mass of NaCl}}{\text{Molar mass of NaCl}}`

`\text{Moles of NaCl}=(520g)/(58.5g/mol)=8.89mol`

Now we have to calculate the number of cups needed.

As, the number of cups needed for 8.89 mole of NaCl = 1 cups

So, the number of cups needed for 4 mole of NaCl =
`(4)/(8.89)=0.45` cups

Thus, the number of cups needed are, 0.45 cups.

Part 2:

Given:

Mass of ice cubes = 1 kg = 1000 g

Now we have to calculate the number of cups needed.

As, the number of cups needed for 220 g of ice = 1 cups

So, the number of cups needed for 1000 g of ice =
`(1000)/(220)=4.5\approx 5` cups

Thus, the number of cups needed are, 5 cups.