7.4 Equations for Chemical Reactions

• If you want to convert between grams and moles, use the molar mass.

• It is used as an expectorant.

• The anesthetic is called CH 3H6.

• C2H5 is used to diagnose dead tooth nerves.

• The characteristic odor of garlic, onions, and leeks is given by 3H5)2S.

• Determine the number of atoms in the reactants and products by writing a balanced chemical equation from their formulas.

• There are chemical reactions that occur everywhere.
• The fuel in a car is used to make a car move and run the air conditioner.
• A chemical reaction happens when we cook food or bleach our hair.
• Chemical reactions in our bodies build muscles.
• The leaves of trees and plants have carbon dioxide and water in them.
• Chemical equations are used to describe reactions.

• When silver tarnishes, the shiny silver metal reacts with sulfur to become a dull, black substance.

• New substances are created with a chemical change.

• A chemical reaction takes place when a piece of iron combines with oxygen in the air to make rust, which has a reddish-brown color.

• Iron nails change color when CaCO3 reacts with acid.

• Adding air with a hot flame causes a yellow solid to form.

• You follow a set of directions when you build a model airplane, prepare a new recipe, or mix a medication.
• The directions tell you what to buy and what materials to use.

• You work in a bicycle shop.

• When you burn charcoal in a grill, the carbon in the charcoal mixes with oxygen to form carbon dioxide.
• A chemical equation can be used to represent this reaction.

• They are separated by plus signs when reacting to form products on the same side.

• They are heated equations.

• When a chemical reaction takes place, the bonds between the atoms of the reactants are broken and new bonds are formed to give the products.
• atoms cannot be gained, lost, or changed into other types of atoms during a chemical reaction.

• 2 atoms of O are given to 4 atoms of H. The H2O formula has a coefficients of 2 in front of it.
• There are 4 hydrogen atoms and 2 oxygen atoms in the products.

• The total number of atoms in a formula is determined by the coefficients of each subscript.

• Carbon dioxide and water are products when ethane, C2H6, burns in oxygen.

• There are 4 C atoms, 12 H atoms, and 14 O atoms in the products.

• The process of balancing a chemical equation is shown in Sample Balancing a Chemical Equation Problem 7.7.

• The gases car Bon dioxide and water are produced by the chemical reaction of methane gas and oxygen gas.
• A balanced chemical equation is needed for this reaction.

• Use the correct formulas for the reactants and products to write an equation.

• There are more H atoms in the reactants and more O atoms in the products when we count them.

• To balance each element, use coefficients.
• The H atoms in CH4 are the most atoms.
• A total of 4 H atoms are obtained by placing a coefficient of 2 in front of the formula for H2O.
• The chemical formula of a reactant or product would be changed if the subscripts were changed.

• We can balance the O atoms on the reactant side by placing a coefficient of 2 in front of the formula O2.
• There are 4 O atoms in the products.

• Check the final equation to make sure it's balanced.

• This is not written correctly because there are equal numbers of atoms on both sides of the equation.
• To get coefficients that are the lowest whole numbers, we divide them by 2.

• Sometimes an equation has the same polyatomic ion in both products and reactants.
• As shown in Sample Problem 7.8, we can balance the polyatomic ion as a group on both sides of the equation.

• Use the correct formulas for the reactants and products to write an equation.

• The equation is not balanced when we compare the number of ion in reactants and products.
• The group of atoms in this equation can be balanced because the phosphate ion appears on both sides of the equation.

• To balance each element, use coefficients.
• We start with the formula that has the highest subscript values.
• The subscript 3 is used to balance magnesium.
• The subscript 2 is used to balance the phosphate ion.

• The reactants and products show that the salts are not balanced.
• To balance the equation, a 6 is placed in front of the NaCl.

• Check the final equation to make sure it's balanced.