Balancing+Equations

Balancing a chemical equation refers to establishing the mathematical relationship between the quantity of reactants and products. The quantities are expressed as grams or moles. It takes practice to be able to write [|balanced equations]. There are essentially three steps to the process: Tin oxide is heated with hydrogen gas to form tin metal and water vapor. Write the balanced equation that describes this reaction. SnO2 + H2 --> Sn + H2O Look at the equation and see which elements are not balanced. In this case, there are two oxygen atoms on the lefthand side of the equation and only one on the righthand side. Correct this by putting a coefficient of 2 in front of water: SnO2 + H2 --> Sn + 2 H2O This puts the hydrogen atoms out of balance. Now there are two hydrogen atoms on the left and four hydrogen atoms on the right. To get four hydrogen atoms on the right, add a coefficient of 2 for the hydrogen gas. Remember, coefficients are multipliers, so if we write 2 H2O it denotes 2x2=4 hydrogen atoms and 2x1=2 oxygen atoms. SnO2 + 2 H2 --> Sn + 2 H2O The equation is now balanced. Be sure to double-check your math! Each side of the equation has 1 atom of Sn, 2 atoms of O, and 4 atoms of H. To do this, you need to be familiar with the properties of various compounds or you need to be told what the phases are for the chemicals in the reaction. Oxides are solids, hydrogen forms a diatomic gas, tin is a solid, and the term 'water vapor' indicates that water is in the gas phase: SnO2(s) + 2 H2(g) --> Sn(s) + 2 H2O(g) This is the balanced equation for the reaction. Online Practice: Movie: http://www.gpb.org/chemistry-physics/chemistry/604
 * BALANCING CHEMICAL EQUATIONS **
 * 1) ** Write the unbalanced equation. **
 * Chemical formulas of reactants are listed on the lefthand side of the equation.
 * Products are listed on the righthand side of the equation.
 * Reactants and products are separated by putting an arrow between them to show the direction of the reaction. Reactions at equilibrium will have arrows facing both directions.
 * 1) ** Balance the equation. **
 * Apply the [|Law of Conservation of Mass] to get the same number of atoms of every element on each side of the equation. Tip: Start by balancing an element that appears in only //one// reactant and product.
 * Once one element is balanced, proceed to balance another, and another, until all elements are balanced.
 * Balance chemical formulas by placing coefficients in front of them. Do not add subscripts, because this will change the formulas.
 * 1) ** Indicate the states of matter of the reactants and products. **
 * Use (g) for gaseous substances.
 * Use (s) for solids.
 * Use (l) for liquids.
 * Use (aq) for species in solution in water.
 * Write the state of matter immediately following the formula of the substance it describes.
 * Worked Example Problem **
 * 1) ** Write the unbalanced equation. **
 * 1) ** Balance the equation. **
 * 1) ** Indicate the physical states of the reactants and products. **

**Review Worksheet for balancing equations Name **
1. Go to Review Chembalancer. ( http://funbasedlearning.com/chemistry/chemBalancer/default.htm) 2. Click ‘Directions’. Read and understand the directions. 3. Click ‘OK’. 4. Click on ‘Start Game’ 5. Try entering some numbers in the text boxes in front of each molecule. What happens? 6. If you forget the directions, click on the ‘How to Play the Game’ link. Click ‘OK’ when you finish reading them to return to the game. 7. When you think you have typed the right numbers in all the boxes, click the ‘Balanced’ button. 8. If you didn’t get it right, try again. 9. If you did get it right, then fill in the correct answers on this worksheet for #1. 10. Repeat steps 7-9 for the other 9 questions. 11. Now do the two problems on the back of this worksheet. You can draw the molecules just like the program did to figure out the answer.
 * Directions:**

=__Questions__= Fill in the blanks below as you go through the game. So I can give you credit for doing your assignment. 1. _ S + _ O 2 --> _ SO 2 2. _ Na + _ O 2 --> _ Na 2 O 2 3. _ Hg + _ O 2 --> _ HgO 4. _ Ag 2 O --> _ Ag + _ O 2 5. _ Ba(OH) 2 + _ H 3 PO 4 --> _ BaHPO 4 + _ H 2 O 6. _ NaOH + _ H 3 PO 4 --> _ Na 2 HPO 4 + _ H 2 O 7. _ C 4 H 8 + _ O 2 --> _ CO 2 + H 2 O 8. _ C 3 H 8 + _ O 2 --> _ CO 2 + H 2 O 9. _ Fe + _ Cl 2 --> _ FeCl 3 10. _ Al + _ HCl --> _ AlCl 3 + _ H 2 Draw the molecules just like the program did to figure out the answer to #11 and #12. 11. _ HgO --> _ Hg + ___ O 2

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