Let say you were given this equation:

NiBr2 + Co = Ni + CoBr2

How can you tell which is liquid,gas,solid,aqueous? Do you just use what you know and figure it out? Like since NiBr2 can be broken down because of the solubility rule, you can assume it aq then Co is a metal so you assume it a solid? Thanks

That's as good as any method I know. It uses what we know about substances. You can look up (or from the solubility rules) that NiBr is aq and you know the metals. There are some common gases. Look at the periodic table--it helps with gases that are elements. H2, N2, O2, F2, Cl2 (or course the noble gases but those aren't involved in chemical reactions.) Then CO2, NO2, N2O4, SO2, SO3, CH4(methane), C2H2(acetylene) and C2H4(ethylene) are rather common. These things get burned into the memory after practice.

To determine the physical state of the substances in a chemical equation, you need to consider their common physical properties and the solubility rules. Here's how you can approach it:

1. Look at the formula: Start by looking at the formulas of the chemical species involved in the equation.

- NiBr2: Nickel(II) bromide is typically a solid at room temperature.
- Co: Cobalt is a transition metal, and in most cases, it is a solid.
- Ni: Nickel is also a transition metal, and like cobalt, it is typically a solid.
- CoBr2: Cobalt(II) bromide is usually a solid at room temperature.

2. Consider the solubility rules: Some compounds have different solubilities in water, which can help determine their physical state.

- Nickel(II) bromide (NiBr2) is typically soluble in water, so it can be assumed to be in an aqueous (aq) state.
- Cobalt(II) bromide (CoBr2) is also soluble in water, so it can be considered aqueous.
- Cobalt (Co) and Nickel (Ni) are metals and are most likely solid in this equation.

Based on the information gathered, you can assume the following physical states for each substance:

NiBr2 (aqueous), Co (solid), Ni (solid), CoBr2 (solid).

Remember that these assumptions are based on typical conditions. In some cases, like at high temperatures or under special circumstances, these compounds may exist in different physical states.