Sodium Carbonate commonly known as Sodium Carbonate is a inorganic compound which used in detergents and to soften the water. Its chemical formula is [tex]Na_{2}CO_{3_[/tex]. It is carbonate base
Lemon juice contain citric acid whose chemical formula is [tex]C_{6} H_{8} O_{7}[/tex]. Citric acid is a weak organic acid thus It is used for disinfectants and cleaning as well.
When Lemon Juice and Washing Soda react, the reaction is just an acid-base reaction and forms trisodium citrate and carbonic acid. The latter is then dissociated into Carbon Dioxide and Water. Carbon Dioxide escapes in the form of bubbles and Sodium Citrate(salt) and Water behind.
(citric acid)+ (sodium carbonate)= (trisodium citrate)+(water)+(carbon dioxide)
[tex]2C_{6}H_{8}O_{7} + 3Na_{2}CO_{3} ---> 2Na_{3}(C_{6} H_{3} O_{7})_{2} + 3H_{2}O + 3 CO_{2}[/tex]