What is the formula mass of ammonium phosphide, (NHsubscript4)subscript3P?

85.0 u
49.0 u
48.0 u
57.0 u

I thought I was to look these up in the Periodic Table, but they aren't there, so I'm confused on what to do. Any help would be appreciated.

To calculate the formula mass of ammonium phosphide, you need to determine the atomic masses of the elements in the compound and then add them together based on their subscripts.

To get the atomic masses of the elements, you can refer to the Periodic Table. However, in this case, the subscripts for both elements are more than 1, which means that the formula given is a polyatomic ion rather than a single atom.

The atomic mass of each element can be found on the Periodic Table as follows:

- Nitrogen (N): 14.01 u
- Hydrogen (H): 1.01 u
- Phosphorus (P): 31.0 u

Now, we will calculate the formula mass of ammonium phosphide:

1. Determine the number of atoms for each element based on their subscripts:
- Nitrogen (N): 3 atoms
- Hydrogen (H): 12 atoms (4 subscripts of 3)
- Phosphorus (P): 1 atom

2. Calculate the mass contribution for each element by multiplying the atomic mass by the number of atoms:
- Nitrogen (N): 14.01 u * 3 = 42.03 u
- Hydrogen (H): 1.01 u * 12 = 12.12 u
- Phosphorus (P): 31.0 u * 1 = 31.0 u

3. Add up the mass contributions from each element:
42.03 u + 12.12 u + 31.0 u = 85.15 u

Therefore, the correct answer is approximately 85.0 u.

To calculate the formula mass of ammonium phosphide, also known as (NH₄)₃P, you need to calculate the sum of the atomic masses of all the atoms in the compound.

First, let's find the atomic masses of the individual elements involved. The atomic masses of nitrogen (N), hydrogen (H), and phosphorus (P) can be found on the periodic table.

The atomic mass of nitrogen (N) is approximately 14.01 atomic mass units (u).
Since there are four hydrogen atoms in each ammonium ion, we will use the atomic mass of hydrogen (H), which is approximately 1.01 u.
The atomic mass of phosphorus (P) is approximately 30.97 u.

Next, let's calculate the formula mass by adding up the atomic masses of each atom.

For ammonium:
(4 hydrogen atoms * 1.01 u) + (1 nitrogen atom * 14.01 u) = 4.04 u + 14.01 u = 18.05 u

For phosphide:
(1 phosphorus atom * 30.97 u) = 30.97 u

Now, let's calculate the formula mass by multiplying the formula mass of ammonium by the number of ammonium ions in the compound:

(3 ammonium ions * 18.05 u) + (1 phosphide ion * 30.97 u) = 54.15 u + 30.97 u = 85.12 u

Therefore, the formula mass of ammonium phosphide, (NH₄)₃P, is approximately 85.12 u.

Out of the given options, the closest value to 85.12 u is 85.0 u.

You DO (REALLY DO) look them up on the periodic table. The periodic table lists elements, not compounds, so you look up the elements and add them.

(NH4)3P. Here are the approximate values but you need to confirm them and make them more exact. I've just used whole numbers.
N = 14 x 3 of them = 42
H = 1 x 12 (that's 4 x 3) of them = 12
P = 31 x 1 of them = 31
Now add 42 + 4 + 31 = formula mass (NH4)3P