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CHM 1025 Exam 2/555 Questions with answers
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CHM 1025 Exam 2/555 Questions withanswers
A chemical reaction is the conversion of one substance or set of substances
into another. - -A chemical reaction is the conversion of one substance or set
of substances into another.
-reactant; product - -Any substance that we start with is a _______ and a
new substance that forms during the reaction is a ______.
-arrangement - -Products are different from reactants in the _______ of their
component atoms.
-chemical - -______ reactions neither destroy atoms nor create new atoms.
They occur because the bonds that hold atoms together can be broken and
rearranged.
-diatomic; slowly; vigorous, even explosive - -Consider the reaction of
hydrogen gas with oxygen gas. Hydrogen and oxygen both occur naturally as
_______ molecules. If they mix, they react _______; but if ignited, the reaction
is _______, even ______.
-gaseous water molecules,
two hydrogen atoms and one oxygen atom. - -in the reaction of hydrogen
gas with oxygen gas, the reactants form the same product: __________
molecules, each containing two ______ atoms and one ______ atom.
-stays constant;
law of conservation of mass (which states that matter cannot be created or
destroyed by ordinary chemical means) - -In every chemical reaction the
number of atoms of each element ________. This is consistent with the law of
conservation of mass
-Sulfuric acid and calcium carbonate are the starting substances, the
reactants. They are converted into carbon dioxide and calcium sulfate, the
products. (Another product is water, which can't be identified from this
description.) - -Breanna mixed a solution of sulfuric acid and solid calcium
carbonate. Carbon dioxide gas bubbled out of the solution as the initial solid
disappeared, leaving behind a deposit of calcium sulfate. Identify the
reactants and products in this chemical reaction.
-they are reactants - -If two elements combine to form a compound, are the
elements reactants or products?
, -reactants are Fe(s) and CuSO4 (aq), products are Cu(s) and FeSO4 (aq) - -
Antonio placed a piece of iron in a solution of copper(II) sulfate. He obtained
a deposit of copper metal and a solution containing iron(II) sulfate. Identify
the reactants and products in this chemical reaction.
-Change in color
Production of light
Formation of a solid (such as a precipitate in solution, smoke in air, or a
metal coating)
Formation of a gas (bubbles in solution or fumes in the gaseous state)
Absorption or release of heat (sometimes appearing as a flame) - -What are
some visible clues that would indicate that a chemical reaction MAY have
occurred?
-A chemical equation - -_________ is a symbolic representation of a chemical
reaction (consisting of chemical symbols and formulas)
-thermite reaction - -When a powdered mixture of aluminum metal and
iron(III) oxide is heated, it reacts vigorously to form liquid iron metal and
aluminum oxide. This reaction is called the_________
-balanced - -when writing a chemical equation it must be a ________
equation, where the number of atoms of each element is the same in the
products as in the reactants.
-coefficients - -When writing chemical equation we indicate the relative
number of molecules or formula units of reactants or products by ________,
which are whole numbers that immediately precede the formula of each
substance.
-smallest possible whole numbers - -The process of balancing an equation
involves examining and modifying coefficients until the reactants and
products contain the same numbers of the component elements. The
coefficients are written as the ____________.
-exist - -The coefficients are whole numbers because parts or fractions of
atoms or molecules do not ________.
-subscript - -It is important to remember that you cannot change the ______
of an element in a compound to balance an equation.
-skeletal equation or an unbalanced equation - -When the atoms of the
reactants and products have not yet been equalized, the equation is called a
______ or __________
, -atoms; molecules - -To balance an equation, we need equal numbers of
_____ of each element on each side of the equation but not necessarily equal
numbers of ______.
-1a). reactants; products
1b). physical state symbols
1c). 1
2a). coefficient
2b). subscripts
2c). coefficients
2d). elemental substances
3. balanced - -Steps for Balancing Equations
1. What is the skeletal equation?
(a) Write correct formulas for _____ on the left side and ______ on the right
side of the arrow.
(b) Include _________ for all substances.
(c)The coefficients (the numbers preceding the formulas) are all _____ in a
skeletal equation.
2. How are atoms of each element balanced?
(a)First look for elements that appear only once on each side of the equation.
If there are different numbers of atoms of that element on each side of the
equation, change the ______ of one or both substances until there is the same
number of atoms on each side of the equation.
(b)Do not change the ______! Changing them in a formula would change the
identity of the substance.
(c)Continue checking all elements in the equation, changing ____ when
needed.
(d)The last atoms to balance should be those in _______ substances (such as
O2), because changing a coefficient in front does not change the numbers of
atoms of any other elements.
3. Is the equation ______? Make a final check by counting the atoms of each
element on both sides of the equation. If they are the same, then the
equation is.
-2KClO3(s) ---heat--> 2KCl(s) + 3O2(g) - -Potassium chlorate is a white solid
that decomposes when heated, forming solid potassium chloride and oxygen
gas. Balance the equation that represents the reaction.
-above the arrow - -If heat must be supplied for the reaction to take place,
or if some other special conditions are needed, we describe them ___________
when writing the chemical equation.
-no, although the atoms are balanced, a correctly balanced equation should
have the lowest possible whole number coefficients - -If all the coefficients in
a chemical equation are divisible by 2, is the equation properly balanced?
, -2Na(s) + 2H2O(l) ---> 2NaOH(aq) +H2(g) - -When sodium metal is dropped
into liquid water, the mixture releases gaseous hydrogen, leaving behind a
colorless solution of sodium hydroxide. Balance the equation that represents
this reaction.
-2C2H6(g) + 7O2(g) --> 6H2O(g) + 4CO2(g) - -Ethane, C2H6, is a gaseous
fuel that can be burned with oxygen. Balance the following skeletal equation
for this reaction: C2H6(g) + O2(g)----> CO2(g) + H2O(g)
-2C4H10(g) + 13O2(g)---> 8CO2(g) + 10H2O(g) - -Liquid butane is often
used as a fuel in cigarette lighters. When the pressure is released, butane
evaporates and can burn with oxygen. Balance the following skeletal
equation for the reaction of butane with oxygen gas.
-ionic; unit - -when part of a reactant is unchanged in the products it usually
arises with ______ compounds in which the anion is an oxoanion or some
other polyatomic anion. If the anion is unchanged in the products, it can be
treated as a _____ instead of as a collection of atoms that must be balanced
individually.
-Zn(s) + 2HNO3(aq) ---> Zn(NO3)2(aq) + H2(g) - -Balance the following
skeletal equation for the reaction of zinc metal with nitric acid:
Zn(s) + HNO3(aq) ---> Zn(NO3)2(aq) +H2(g)
-alkali metals; vigor - -The __________ all react with water to form the
corresponding alkali metal hydroxide and hydrogen gas. The pattern of
rearrangement is the same for all of these reactions. They differ only in their
_____.
-the corresponding alkali metal hydroxide and hydrogen gas - -The alkali
metals all react with water to form ______ and _____
-metal hydroxide and oxygen gas - -Alkaline earth metals react in a similar
way, producing a ____ and _______
-periodicity - -The principle of _____ suggests that the other alkali metals,
like lithium metal, will also react with water to form a metal hydroxide and
hydrogen gas.
-potassium; explosive - -all of the alkali metals react with water; what
differs is the vigor of the reaction. With the ______ reaction, the hydrogen
always catches fire and for the alkali metals below it in the periodic table,
the reaction with water is ____.
-monatomic; diatomic - -consider the case in which we have just one
reactant- we probably have to heat the substance for something to happen.
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