If a certain compound has a formula xcl₃ what is the valency of x?

The general form of a compound can be written in the form of:

[X(a) Y(b)] ^ c

Where a and b are subscripts, and c is the superscript of the whole formula.

The relationship that we can derived here between the constants is:

(valence of X) * a + (valence of Y) * b = c

Since the formula obviously has no superscript, therefore c = 0. We also know in chemistry class that the valence of Cl is -1, therefore:

valence of X * 1 + (-1) * 3 = 0

valence of X - 3 = 0

valence of X = 3

1. 1 mole of anything contains 6.022x10^23 pieces  

d  

2. a  

3. c, number  

5. 1.24x10^24atoms / 6.022x10^23atoms/mole = 2moles h2 atoms  

6. fe2br3 mass = 2moles x mass fe + 3 moles x mass br  

molar mass = grams / number of moles = g/mole  

to find moles = g / molar mass  

to find mass = g = molar mass / moles