Determine the number of NH4+ ions in a 145 g sample of (NH4)2SO4.

To determine the number of NH4+ ions in a sample of (NH4)2SO4, we need to use Avogadro's number and the molar mass of (NH4)2SO4.

Here's how you can calculate it:

Step 1: Find the molar mass of (NH4)2SO4.

(NH4)2SO4 consists of two NH4+ ions and one SO4^2- ion. The molar mass of NH4+ ion is 18.039 g/mol, and the molar mass of SO4^2- ion is 96.07 g/mol.

So the molar mass of (NH4)2SO4 can be calculated as:

[(2 NH4+) + (1 SO4^2-)] = [(2 x 18.039 g/mol) + (1 x 96.07 g/mol)]
= 132.139 g/mol

Step 2: Calculate the number of moles of (NH4)2SO4 in the sample.

To calculate the number of moles, divide the mass of the sample by the molar mass of (NH4)2SO4:

Number of moles = Mass of sample / Molar mass
= 145 g / 132.139 g/mol
= 1.097 moles

Step 3: Calculate the number of NH4+ ions in the sample.

Since there are two NH4+ ions in one mole of (NH4)2SO4, we can calculate the number of NH4+ ions as:

Number of NH4+ ions = Number of moles x 2
= 1.097 moles x 2
= 2.194

Therefore, there are approximately 2.194 x 10^23 NH4+ ions in the 145 g sample of (NH4)2SO4.

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