# Tag Info

Accepted

### How can there be decimal subscripts in a molecular formula?

First of all, in chemistry two types of formulas exist: structural and empirical. A structural formula shows the way atoms are connected. An empirical formula only summarizes atoms and their ratios. ...
• 20.6k

### Do coefficients matter in rate law?

This confusion pops up often around here. The problem usually comes down to insufficient consideration of units. When you say "rate", what do you mean? It has units of mol per volume per second, ...
• 20.2k

### Why can't I balance this reaction algebraically?

Here's how to solve the system in python: ...
• 20.2k
Accepted

### Are matrices a good way to do stoichiometry?

Sure, most of the equation-balancing Javascript calculators on the web use that method. It's overkill to balance a single equation that way, but if you're automating the process or if you have a lot ...
• 5,457
Accepted

### CH4 + O2 => CO2 + 2H2, what's wrong with it?

The reaction as you state it is correct only if there will react only one molecule of oxygen. But the reaction describes burning of methane which is supposed to be in the presence of excess of oxygen. ...
• 2,135
Accepted

• 65.6k

### Unknown notation relating to stoichiometry

It is probably supposed to be the 'corresponds to' sign[ref, p 105]; in this case simply representing that for every two moles of $\ce{NaOH}$ one mole of $\ce{H2SO4}$ is converted by reaction ...
• 6,851
Accepted

### What does n(Na2CO3) mean?

Yes, the standardized quantity symbol according to ISO 80000-9:2009 Quantities and units — Part 9: Physical chemistry and molecular physics as well as the recommended quantity symbol according to ...
• 2,228
Accepted

### Is this definition of mole correct?

The mole is a base unit as specified in the Système international d’unités (SI) by the bureau international des poids et mesures. Its decisive definition is that published in French: La mole est ...
• 63.6k
Accepted

### Unknown notation relating to stoichiometry

The sign $≏$ is read "is chemically equivalent to". The term chemically equivalent refers to a specific chemical reaction. For the reaction $$\ce{N2(g) + 3 H2(g) -> 2NH3(g)}$$ \pu{1 mol } \ce{N2} ...
• 1,308

### More than one way of balancing a chemical equation

This happens when you have a sum of two (or more) independent reactions. You can balance each one, and then add them together in an arbitrary proportion. People usually run into this when trying to ...
• 29.6k

• 10.5k
Accepted

### How much sulphuric acid can be obtained from 5 kg of sulfur

$\ce{S6}$, $\ce{S8}$, $\ce{S12}$ – does it make a difference or is it just a trick to make the question more complicated than it is? What you know for sure is: \$M(\ce{S}) = 32.065\ \mathrm{g}\cdot \...

### After completing an experiment, a student finds that the percentage yield exceeded 100%. What could have occurred to the sample to lead to this?

Below is a basic example. If percent yield is based on a mass, then a >100% yield can result from a product contains materials that should not be there. For instance, a product that should be ...
• 4,549

### What is the difference between ''1 C atom and 1 mole of C atoms?''

What is the difference between one egg and one dozen eggs? A dozen is simply a certain count, in this case 12, that is rendered as one unit for our convenience. Avogadro's number s just the same ...
• 38.1k
Accepted

### When are we justified in making assumptions in questions

You can make certain assumptions in these and similar problems because concentration of uniform substances (whether it's expressed as molarity, molality, mass density, or something else entirely) is ...
• 11.6k
Accepted

### After completing an experiment, a student finds that the percentage yield exceeded 100%. What could have occurred to the sample to lead to this?

Preface: The problem is that you have overstated your percentage yield, and the symptom is that it is above 100%. Example: You and your friend each do an experiment where the literature states the ...
• 206
Accepted

### Error in formula for the solution to a chemical problem

The equation is a little dubious, as I mentioned in the comments. How do we come up with coefficients of this sort? Let's go from scratch. We don't know the coefficients at this point so we'll ...
• 65.6k
Accepted

### Balancing the reaction equation for the oxidation of lead(II) sulfide with ozone

This is a semi-standard example of why 'naive' balancing does not work. Ozone is a source of atomic oxygen, producing free oxygen molecules. So, in 'mild' conditions only one oxygen per ozone ...
• 20.6k