Several questions about formulae

[Fallacy202]

Okay, here are several seemingly very simple questions but I've never found out the answers to:

1. Does hydrogen ever bond ionically with non-metals (you're taught in HS that they do). If they do, how do you tell an ionic hydrogen compound from a covalent hydride?

2. Combustions w/o hydrocarbons. How do you determine them? Are all reactions with a O2 on the left combustions? What about 2H2 + O2 yields 2H2O?

3. How do you determine the charge of a transition metal in the product given only the reactants? So for example:

copper + acetic acid would yield ?

My teacher taught me in HS that it should be copper acetate, but what's the charge on Cu here?

Thx to anyone that could answer any of my questions. They're fairly simple to some of you I'm sure, but I'm dumbfounded.

[akcapr]

1. yes it does very often as in HCl or H2SO4

2. ya.. combustions dont need O2. combustion is just exothermic reaction between a fuel and oxidizer.

3. u can remebrr the charge on acetate then balnce it wth the copper charge

[jdurg]

1. yes it does very often as in HCl or H2SO4

2. ya.. combustions dont need O2. combustion is just exothermic reaction between a fuel and oxidizer.

3. u can remebrr the charge on acetate then balnce it wth the copper charge

 

1): That is not correct. The bonds in HCl and H2SO4 are 100% covalent bonds. The bonds are broken apart in the presence of water, but the pure substances are NOT ionic. If they were, then HCl and H2SO4 would both be crystals at room temperature and pressure due to the ionic charges they exhibit. As you should be well aware, HCl is a gas and H2SO4 is a syrupy liquid. I do not know of any compound involving hydrogen and a nonmetal where the bonds involved can be classified as ionic.

 

2): In a combustion reaction, the most electronegative species is the oxidizer and the least electronegative species is the fuel. Generally speaking, however, 'combustion' is typically reserved for hydrocarbons or hydrogen combination with oxygen in order to prevent confusion. When the oxidizer isn't oxygen, it's typically just called a redox reaction.

 

3): How would he know if it's copper (I) or copper (II). Also, how would he determine the formula for a reaction between chromium and acetic acid? To know what will form and in what oxidation state, your pretty much just have to memorize it. (Though you could look up the reduction potential of acetic acid and the reduction potential of the metal that you're reacting. Then just see what is more likely to happen based on the values. If the metal can easily be oxidized to the +2 state, then you'll have a formula of Metal(CH3COO)2)

[Fallacy202]

Thanks a lot for the quick responses.

2) Are all reactions with oxygen combustion reactions? Err, maybe no one noticed it, but is 2H2+O2->2H2O a combustion reaction? I'm still not very clear on how to classify a reaction as a combustion reaction.

3) Can copper combine with acetate to form copper (I) acetate and copper (II) acetate both? Or is it more likely to combine in one way? If so, which one is it?

thanks a lot.

[woelen]

Thanks a lot for the quick responses.

2) Are all reactions with oxygen combustion reactions? Err' date=' maybe no one noticed it, but is 2H2+O2->2H2O a combustion reaction? I'm still not very clear on how to classify a reaction as a combustion reaction.[/quote']

I would call any reaction, where fire is involved a combustion, so your example also is. But, there are more possibilities, even without oxygen involved. The gas H2 can burn in an atmosphere of Cl2. I myself once burnt a candle in an atmosphere of Cl2, where it burns with a red flame, giving HCl and soot.

 

 

3) Can copper combine with acetate to form copper (I) acetate and copper (II) acetate both? Or is it more likely to combine in one way? If so, which one is it?

thanks a lot.

As jdurg wrote, you have to memorize. In the case of copper, it forms copper (II) acetate. Copper (I) compounds can be formed, but the conditions for these must be quite specific. As a first step, just memorize that copper metal forms copper (II) ions in aquous solutions with almost all cations.