How to type Chemical equations with a Keyboard?

Dear sir, you can easily type chemical equation by using the HTML tag. For typing an equation you should use sub-HTML tag.
For example:
Hydrogen and water combines to form water.
2H(use sub tag here) + O Sub tag again = 2H(sub tag)O

to use sub tag:
< sub > number of molecules < /sub >
Note: No space should be entered while writing sub tag.

If you want to type an equation in MS word it is very easy. Go to insert menu. Here you will find the equation at very last. Click here and you would be able to type an equation.
I have type chemical equation in one of my articles: How to balance a chemical equation? Please refer it.

Hope this answer would be helpful to you.

You can do it in Google docs also. You can try as mentioned below.
1, A document in Google Docs is to be opened
2. Please click in the place where you want to write the equation.
3, Then you have to click on Insert
4. You will see a list. Click on Equation.
5. You can select, Select the symbols you want to add from one of these menus:
Greek letters
Miscellaneous operations
Relations
Arrows
Add numbers or substitute variables in the box.

You can easily write chemical equations using Microsoft word.
You can use the latest version of Microsoft word app in Phone and it's free to access, but when you are using computer or laptop to write the chemical equation, you can only access freely the earlier version of MS word 2007 and in the latest version you have to purchase the license to use in Computer. But you can freely access MS word online without downloading the software on your computer, go to google and search "Microsoft word online", you can find Microsoft word live access website, but you have to sign-in before you use it. You can copy and paste the chemical equations from MS Word wherever you want.
There are some steps to be followed to write a chemical equation in MS Word and the steps vary for android and computer.

How to write a chemical equation using MS Word in Computer:
For example, if you want to type the chemical equation like
"CH4 + O2 -> CO2 + H2O".
Two methods to write the chemical equation:-
1) Simple method: (Prefer when you use this type of equation only)
Type CH4 and click "Shift + left arrow" it selects "4" and press "Ctrl ++", it subscript(Print below the line)the letter you select.
Similarly type O2, CO2, and H2O. If you want to use superscript(Print above the line) Click "Ctrl+Shift+ +". For typing arrow (->), see another method.

2) Another method: (Prefer when you use more types of the chemical equation)
You can insert the equation by selecting "Insert -> Equation -> Insert New Equation". A new box appears with the text "Type equation here". Here you can type equation by using letters or symbols and the word converts into the equation.
CH4 as, 4 as a subscript to CH(4 in below CH) – type CH_4 and click "Space", it converts to CH_4 as 4 as a subscript to CH(4 in below CH).
As similar, if you want to add the equation by O2, Click "+" and Type O_2 and click "Space", it converts it to 2 as a subscript to O(2 in below O).
The equation you type looks like "CH_4(Space) + O_2(Space)"(MS word convert it into the chemical equation).
And then add arrow by selecting "Design -> --> "(Select "Design" after clicking the "insert new equation" option from "Equation", then only the option appears). And then type like CO_2(Space) + H_2(Space)O.
Finally, the equation looks like a chemical equation as you want.
If you want to use superscript, you can use "^" instead of using "_" in subscript.

Hint: For Subscript you have to use "_" and for Superscript you have to use "^" only in Equation box.

For the heat equation, Delta symbol is in the above and the arrow symbol in the middle or below delta is required. For that, you have to select "Design -> Operator, and select delta from Common operator structure".

You can simply type the equations and you can convert into the chemical equations by using Find and Replace option. You can edit the number of subscript and superscript by selecting the all you want to convert, in Find and Replace option.

How to write a chemical equation using MS word in Android Phone:
1) Simple method:
Type the chemical equation you want and select the letter which you want to Subscript or Superscript. Example: For CH4, select 4 and click the "Bulb" icon, that displays above the keyboard at the right corner, and search or type "subscript or superscript". The letter turns to subscript or superscript.
2) Alternate method:
For the alternate method, refer to the above alternate method which is used in the computer. You can find or search "Equation" in the Bulb icon. After clicking "Equation" the Equation box appears. After that, for subscript, you can use "_" and for superscript, you can use "^" keys.

With the application of MS Word, the equation can be written.
First of let us go to the insert tab with the pressing of Alt+= together.
Let us click the equation button available on the far right.
The equation should be typed using the button in the ribbons.
Alternatively, we can use _ for subscript and ^ for superscript.
To get a long arrow, we should click on the operator choosing the arrow with the application of word Yield appearing under the common structure.
Click the word Yield and replace the same as needed to create an arrow of the matching length we want.