## Writing out equations

LeAirraBullingor2k
Posts: 77
Joined: Wed Mar 13, 2019 12:15 am

### Writing out equations

On questions like problem H3 on the homework this week, I was wondering if there was a specific order we should write our equations in? For example, would it matter if it was SiH4 or H4Si. It's been a minute since I've taken a chemistry class so I cant remember.

Amanda Lin 2I
Posts: 101
Joined: Sat Aug 17, 2019 12:15 am

### Re: Writing out equations

There is an order to the elements in chemical formulas due to the Hill System. Carbon comes first, next is hydrogen, and then it is the rest of the elements alphabetized. There are also exceptions to this rule.

Posts: 51
Joined: Sat Sep 07, 2019 12:19 am

### Re: Writing out equations

Usually when writing the formula for compounds, you write the cation (atom that is positively charged and this is usually a metal) followed by the anion (atom that is negatively charged and this is usually a nonmetal). In the case of SiH4, Si should be written first since it a metal that has a charge of +4 (cation), while hydrogen should come after since it is a nonmetal that has a charge of -1 (anion).

LeAirraBullingor2k
Posts: 77
Joined: Wed Mar 13, 2019 12:15 am

### Re: Writing out equations

In which cases would it be based on charge and when would it just be based on the order?

Arianna Perea 3H
Posts: 50
Joined: Thu Jul 25, 2019 12:17 am

### Re: Writing out equations

Are we expected to know the molecular formulas of certain compounds for the test or will it be given to us?

Nohemi Garcia 1L
Posts: 103
Joined: Fri Aug 02, 2019 12:15 am

### Re: Writing out equations

I think some of the molecular formulas are given to us, such as the "less common ones", whereas compounds like carbon dioxide which are "more common" will not.

Posts: 51
Joined: Sat Sep 07, 2019 12:19 am

### Re: Writing out equations

There is a specific order when writing out chemical formulas. For instance, C6H12O6 (glucose) is never written like H12O6C6. Out of convention, carbon is always the first atom to be listed in chemical formulas and hydrogens are next. Other atoms are listed alphabetically thereafter.

TarynD_1I
Posts: 100
Joined: Sat Aug 24, 2019 12:17 am

### Re: Writing out equations

According to the Hill System, you're supposed to put C carbon first, then Hydrogen, then all the other elements in alphabetical order. But if there is no Carbon the formula, then all the elements are written in alphabetical order.

Posts: 49
Joined: Wed Sep 18, 2019 12:20 am

### Re: Writing out equations

When writing out equations is it always necessary to include the states of matter (if not specified in the problem)? Thank you:)

Jacob Villar 2C
Posts: 105
Joined: Sat Aug 17, 2019 12:18 am

### Re: Writing out equations

The Hill system shows that the order of listing elements starts with carbon atoms, then hydrogen atoms, and then all other atoms in alphabetical order.