Answer:
1.16mol of NaCl
Step-by-step explanation:
Question:
1. How many formula units are in 67.69 grams of salt?
2. How many molecules are in 44.99 grams of water?
Converting mass to moles:
In a given amount of moles (n) of a substance there will be a given amount of mass (m) of that substance. m and n are related by the molar mass (M):
m = n x M
Hence, if we want to find n, we must rearrange the equation:
n = m/M
Answer and Explanation:
The word 'salt' in this question will be assumed to mean table salt - sodium chloride, NaCl - with a molar mass of 58.44g/mol.
Hence, 67.96g will contain 67.69g / 58.44g/mol = 1.16mol of NaCl.
We convert from moles to number of molecules/formula units by multiplying by Avogadro's constant(6.02×10²³):
1.16 x 6.02×10²³ = 6.98×10²³
formula units of NaCl
Water has a molar mass of 18.02g/mol. Therefore, 44.99g of water will represent 44.99g / 18.02g/mol = 2.50mol of water.
2.50 x
6.02
×
10
23
=
1.505
×
10
24
molecules of water