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Chem - Chap 8
Section 1 - Describing Chemical Reactions
Question | Answer |
---|---|
The process by which one or more substances are changed into one or more different substances. | Chemical reaction |
In any chemical reaction, the original substances are known as | Reactants |
In any chemcial reaction, the resulting substances are known as | products |
The total mass of reactants must equal the total mass of products for any given chemical reactions | The law of conservation of mass |
Represents with symbols and formulas the identities and relative molecular or molar amounts of the reactants and products in a chemical reaction. | Chemical Equation |
Changes which usually indicate that a chemical reaction has occurred. | 1. Evolution of energy as heat and light 2. Production of a gas 3. Formation of a precipitate 4. Color change |
True or False: Heat or light by itself is not necessarily a sign of a chemical change because many physical changes also involve either heat or light | True |
A solid that is produced as a result of a chemical reaction in solution and that separates from teh solution | precipitate |
What aides you in writing and reading chemical equations correctly | 1. The equation must represent known facts. 2. The equation must contain the correct formulas for the reactants and products. 3. The law of conservation of mass must be satisfied. |
A small whole number that appears in front of a formula in a chemical equation. | coefficient |
Placing a coefficient in front of a formula specifies | The relative number of moles of the substance |
if no coefficiet is written, the coefficient is assumed to be | 1 |
An equation in which the reactants and products in a chemical reaction are represented by words | Word Equation |
The first steps in writing in a chemical equation is | Identify the facts to be represented |
A word equation has only what type of meaning | Qualitative (descriptive) |
In a word equation the arrow is read as | react to yield or yield (also produce or form |
Represents the reactants and products of a chemical reaction by their symbols or formulas. | Formula equation |
In a formula equation the g in parentheses after each formula indicates | The corresponding substnce is in the gaseous state |
The relative amounts of reactants and products represented in the equation must be adjusted so that the numbers and types of atoms are the same on both sides of the equation is called | Balancing the equation |
To balance the equation, beagin by | Counting atoms of elements that are combined with atoms of other elements and that appear only once on each side of the equation |
Changing the subscripts of a chemical formula changes the | identity of the compound |
An arrow pointing up indicates | Gaseous product |
A downward arrow is often used | To show the formation of a Precipitate during a reaction in solution |
Indicates the reactants must be heated | The word heat symbolized by a Greek capital delta |
A substance that changes the rate of a chemical reaction but can be recovered unchanged | Catalyst |
A chemical reaction in which the products re-form the orignal reactants. | Reversible reaction |
Writing two arrows pointing in opposite directions | Reversible reaction |
A (s) in parenthesis is used to indicate | a reactant or product in a solid state; also used to indicate a precipitate |
A (l) indicates | A reactant or product in a liquid state |
A (aq) indicates | A reactant or product in an aqueous solution (dissolved in water) |
An Arrow with 2 atm above it indicates | Preassure at which reaction is carried out in this case 2 atm |
An arrow with the word pressure written above it indicates | Preasure at which reaction is carried out exceeds normal atmospheric pressure |
An arrow with 0 degrees C above it indicates | Teh temperature at which reaction is carried out in this case 0 degrees C |
An arrow with MnO2 above it indicates | Formula of catalyst, in this case manganese dioxide, used to alter teh rate of the reaction |
Write word & balanced chemcial equations for Solid calcium reacts with solid sulfur to produce solid calcium sulfide | Calcium + sulfur --> calcium sulfide; 8Ca(s) + Sg(s) --> 8CaS(s) |
Write word & balanced chemical equations for Hydrogen gas reacts with fluorine gas to produce hydrogen fluoride gas | Hydrogen + Floride --> hydrogen fluoride; H2 (g) + F2(g) --> 2HF(g) |
Write word & balanced chemical equations for Solid aluminum metal reacts with aqueous zine chloride to produce solid zinc metal and aqueous aluminum chloride | Aluminum + zinc chloride --> zinc + aluminum chloride; 2Al(s)+3ZnCl2(aq)-->3Zn(s)+2AlCl3(aq) |
The arrow in a balanced chemical equation is like an | Equal sign |
Significance of chemical equation: The coefficients of a chemical reaction indicate relative, not absolute | amounts of reactants and products |
Significance of chemical equation: The relative masses of teh reactants and products of a chemical reaction can be determined from | The reaction's coefficients |
Significance of chemical equation: The reverse reaction for a chemical equation has the same | relative amounts of substances as the forward reaction |
Step 1 to balancing chemcical equations | Idedntify the names of the reactants & the products and write a word equation. |
Step 2 to balancing chemical equations | Write a formula equation by substituting correct formulas for the names fo the reactants adn te products |
Step 3 to balancing chemical equations | Balance the formula equation according to the law of conservation of mass |
Step 4 to balancing chemical equations | Count atoms to be sure that the equation is balanced |
Write the word, formula, and balanced chemical equation for Solid magnesium and aqueous hydrochloric acid react to produce aqueous magnesium chloride and hydrogen gas | Magnesium cloride + hydrochloric acid -->magnesium chloride + hydrogen; Mg(s) + HCl(aq) -->MgCl2(aq) + H2(g); Mg(s) + 2HCl(aq)-->MgCl2(aq)+H2(g) |
write the word, formula and balanced chemical equation for Aqueous nitrick acid reacts with solid magnesium hydroxide to produce aqueous magnesium nitrate and water | Nitric acid + magnesium hydrogen -->magnesium nitrate + water; HNO3(aq) + Mg(OH)2(s)--> Mg(NO3)2(aq)+H2O(l); 2HNO3(aq)+Mg(OH)2(s)--> Mg(NO3)2(ag) + 2H2O(l) |