Xreact.org was intended not only as your source for chemical equations, but also as an instrument to help you with the routine chemistry problems solving. Below you will see few examples of how you can use this system effectively. All forms on this page are operational so go ahead and push some buttons.

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### 1. Measure units used by the engine

Currently this service can make calculations with the following units of measure:

Atomic mass unit (molecular mass): Dalton (Da) which equals to 1/12 of a mass of 12C nucleus.

Mass: metric gram (g) only.

Volume: metric litre (l).

Amount of substance: mole (Mol).

### 2. Finding chemical equations with the search form on homepage

Depending on the user input into the form on the main page, the system can do 3 things. If you type in something like “compound1 + compound2” then the system will search for the equations where the indicated compounds are present in the left part of the equation. If the user input starts with the “=” sign like “= compound1 + compound2” then the system will search for the equation where indicated compounds are in the right part of equation. If the user types-in full equation like “compound1 + compound2 = compound3” or “compound1 + compound2 = compound3 + compound4” then such string is recognized as a chemical equation that the user wants to submit to the page.

Searching for equations. The main feature of this site is a storage and retrieval of chemical equations. For example you want to know what happens when Hydrogen and Oxygen combine. Simply type in the text field on the main page “H2 + O2”: Example 1.

You will notice that the results returned to you are divided in two groups separated by the horizontal line. The results above the line match your inquiry more strictly then the results below the line. This was implemented to help you find the equation you need even if you don’t know the exact formula or indexes in a compound formula. For example you could’ve just typed in “H + O” for an example above or instead of searching for “Ca(OH)2” you can search for “CaOH” and the engine would still find you chemical equations with correct formulas. The drawback of alternative search algorithm is that sometimes it returns too many results. If there were no results then site will put whatever you wrote into database to be reviewed later.

You can also search equation if you know any compound from its right part. For example you know that during certain process the alcohol “C2H5OH” is formed. Simply type in the compound into the search bar starting from equal sign: Example 2.

The engine will return to you chemical equations where “C2H5OH” is present in the right part of equation.

If you type in full equation with the right part and the left part then the system will simply insert it into the database as it is.

The equations that are RED were submitted by users but are still to be confirmed correct.

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### 3. Molecular (molar) mass calculator

Molar mass calculations are available on the corresponding page. Unlike most molar mass calculators around the web, this one offers more options. Lets see the example problems.

Problem: what is the number of molecules and the mass in exactly 42,4 mol of silver nitrate AgNO3?

To solve this problem, you only need to insert the known value, its unit of measure and the compound formula into the form: Example 3.

The system will calculate the rest for you, just try it out!

Problem: what is the mass and the amount of substance of 25 ? 10^{23} carbon dioxide molecules?

Again the only thing you have to do is to put the known values into the form: Example 4.

Yet again the system will calculate the rest for you.

If you are given compound mass then the just do like in the examples above but check “mass, g” radio button.

### 4. Proportion-based chemical problems

Perhaps the most common chemical problems in schools are proportion-based chemical problems. To successfully solve one of these you will need a correct chemical equation relevant to the problem. Lets solve a typical problem step by step.

Problem: What volume of carbon dioxide was produced during the alcohol fermentation of glucose with a mass of 500g?

First of all we need chemical equation relevant to the problems so lets find it. We can search either by glucose in the left part of equation or by alcohol (like in example 2) and/or carbon dioxide in the right. Lets search by glucose. The results page will show us something like this: Example 5.

As we can see, the most relevant to our problem is the chemical equation number 542. Lets check it and press “Solve a problem with equation” button. The engine will take us to another form. So we must find the volume of carbon dioxide, lets put “?” over it in equation and set the menu to “V, l”. Lets also put the known mass of the glucose (it was 500 grams, remember?) and set the menu to “m, g”. Please note that you can fill fields above of only any two compounds in the equation.

Now we have effectively instructed the engine of what we know and what we want to know. Lets leave rest of the form untouched, push “Solve!” button and see what happens: Example 6.

As you can see, the system had not only calculated the result, but also displayed calculations process for you.

If you notice any bug or have a suggestion to make, please go to contacts page.

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