balancing

[Frozen]

Hi, I recently went back to college and Chemistry seems to be really giving me a run. I've been out of school for 20+ years and I'm struggling. Currently we are working on balancing equations, I understand the process and can get through the "easier" ones. The ones that I seem to struggle with the most involve subscripts and when to use parentheses. Is there a secret to this madness? Any tips? I swear I've watched every video online. I've been using the calculator tool provided to check my work and I can't seem to understand how it travels. I hope this makes sense.

Thank you

[ChenBeier]

Give an example what you don't understand.

[Frozen]

Ca + H₃PO₄

Supposed to identify type of reaction, full in the products and balance

The answer is Ca₃(PO₄)₂ + H₂

I cant figure out how/why the subscripts and parentheses appear.

Sorry if that doesn't make sense

[ChenBeier]

Ca + H₃PO₄ => Ca₃(PO₄)₂ + H₂

So you see the Calciumphosphate contain 3 Ca, means you need them in the equation.

3 Ca + H₃PO₄ => Ca₃(PO₄)₂ + H₂

You also can see it contain 2 Phosphates, means you need 2 Phosphoric acid.

3 Ca + 2 H₃PO₄ => Ca₃(PO₄)₂ + H₂

At the end you count the hydrogen. On left side you have 6. On right side you need also 6, what means 3 H₂ will be developed

3 Ca + 2 H₃PO₄ => Ca₃(PO₄)₂ + 3 H₂

Finished.

[Frozen]

In the answer how does Ca become Ca₃ ? That's where I'm unsure. Or why does PO₄ suddenly get parentheses?

[Frozen]

I apologize if this seems like a silly question. We just started this equation stuff and have an exam on it already next week. I'm just trying to grasp the basics to at least pass

[ChenBeier]

Calcium stand in the second group in the PSE. Means it is bivalent. Phosphate is an Anion what is trivalent. You can see it in Phosphoric acid it contain 3 H. H is monovalent.
The PO₄ as a fixed unit has to be in parenthesis therefore.
Calcium can connect 2 single bonds, Phosphate 3. Means you need 3 Calcium gives 6 bond and 2 Phosphates gives also 6 bond.
The Formula is Ca₃(PO₄)₂

[Frozen]

Oh that's a lot to take in, I will keep trying. I truly appreciate the guidance. Thank you

[Violetica]

Calcium stand in the second group in the PSE. Means it is bivalent. Phosphate is an Anion what is trivalent. You can see it in Phosphoric acid it contain 3 H. H is monovalent.
The PO₄ as a fixed unit has to be in parenthesis therefore.
Calcium can connect 2 single bonds, Phosphate 3. Means you need 3 Calcium gives 6 bond and 2 Phosphates gives also 6 bond.
The Formula is Ca₃(PO₄)₂

[Violetica]

I like very much how you explain about balancing and it’s very useful. Thanks !