The document discusses balancing the chemical equation KClO3 → KCl + O2. It explains that chemical equations must be balanced according to the law of conservation of mass. To balance this equation, coefficients are placed in front of the chemical formulas to make the number of atoms of each element equal on both sides. Placing a coefficient of 2 in front of KClO3 and 3 in front of O2 balances the numbers of oxygen, potassium and chlorine atoms. Therefore, the set of coefficients that correctly balances this equation is 223.

1. Chemistry Item 02-03 Which set of coefficients correctly balances the equation KClO 3  KCl + O 2 ? A. 111 B. 123 C. 223 D. 323 www.upcatreview.com

2. Chemistry Item 02-03 CONCEPT : A chemical equation shows the kind and amount of substances that took place in a chemical reaction represented by symbols and formulas. For chemical equations to represent a chemical reaction correctly, it is important to write the correct formula for the reactants and the products and then balanced to be consistent with the law of conservation of mass. www.upcatreview.com

3. Chemistry Item 02-03 To balance the equation would mean that each side of the equation has equal number of atoms of each element. When balancing equations, it is important to note that the identity of the atoms must not be changed thus the subscripts of the chemical formula must never be changed nor can atoms be added or subtracted from a formula. Some important reminders when balancing an equation are as follows: www.upcatreview.com

7. Chemistry Item 02-03 Balancing the reaction given in the previous problem, KClO 3  KCl + O 2 www.upcatreview.com

8. Chemistry Item 02-03 The most complicated molecule is KClO 3 . Balancing can begin by inspecting the product that contains the atoms in KClO 3 . The no. of atoms for both K and Cl are already equal except for oxygen. The left side has three atoms of oxygen while only 2 on the right side. www.upcatreview.com

9. Chemistry Item 02-03 Usually, this set of coefficients is balanced by writing a coefficient of 3 before the oxygen on the right side then a coefficient of 2 is placed before KClO 3 making the number of oxygen atoms 6 for both sides. www.upcatreview.com

10. Chemistry Item 02-03 2 KClO 3  KCl + 3 O 2 (6 O atoms) (6 O atoms) (2 K atoms) (1 K atoms) (6 Cl atoms) (1 Cl atoms) www.upcatreview.com

11. Chemistry Item 02-03 And since the balancing of oxygen atom affected the number of K and Cl atoms on the left side, a coefficient of 2 is added before KCl on the right to balance the equation. www.upcatreview.com

12. Chemistry Item 02-03 Now check the equation: 2 KClO 3  2 KCl + 3 O 2 (6 O atoms) (6 O atoms) (2 K atoms) (2 K atoms) (2 Cl atoms) (2 Cl atoms) www.upcatreview.com

13. Chemistry Item 02-03 Thus the final answer would be 2 KClO 3  2 KCl + 3 O 2 ( equation is balanced ). The summary of coefficients is 2 2 3 ( letter C ). www.upcatreview.com