CHEM 100 - EXAM #2 Questions And
Answers Solved Solution Guaranteed
what happens to the KE of a moving bus as it comes to stop? - correct answers it is converted into heat
an example of an endothermic process is:
A.) digestion of food
B.) burning of coal
C.) melting of ice
D.) all of the above - correct answers C
in an experiment, if the initial temperature is 72.1C and the final temperature is 26.9C, what is the
temperature change for this experiment? - correct answers -45.2C
in which of the following is energy (heat) released?
A.) evaporation of water from your skin
B.) conversion of carbon dioxide gas into dry ice (solid carbon dioxide)
C.) digestion of food
D.) all of the above
E.) only B and C - correct answers E
if 25g of iron (c=.45J/gC) and 25g of silver (c=.24J/gC), both at room temperature, are dropped into
separate glasses of 50 mL of water at 90C, which metal will reach the higher temperature? explain. -
correct answers silver
how does the amount of energy needed to heat a sample of water from 16C to 42C compare to that
needed to heat this same sample form 51C to 77C? explain. - correct answers the amount of thermal
energy (heat) is the same since the same sample (same mass and specific heat) is undergoing the same
temperature change (change in temp is 26C)
,a 280g metal bar requires 5.31kJ to change its temperature from 21C to 100C. what is the specific heat
of the metal - correct answers .24J/gC
Consider a sample of water in the gaseous state. Describe what happens to the molecules in the sample
as the sample is slowly cooled until it liquefies and then solidifies. - correct answers As water molecules
in the gas phase are cooled they begin to slow down and eventually interact strongly enough so that
they can only move around each other as the liquid state forms. Further cooling causes the molecules to
move even more slowly, eventually forming a 3-dimensional arrangement (lattice) in which each
molecule is locked into place by its strong attractions to other molecules as the liquid freezes.
What important idea is behind the practice of writing balanced chemical
equations? - correct answers Atoms are neither created nor destroyed in chemical reactions.
Convert each of the following word equations into a chemical equation and then balance it. Indicate the
physical state of each reactant and product.
A.) sodium metal + oxygen gas -> sodium oxide
B.) sodium bicarbonate -> sodium carbonate + water + carbon dioxide
C.) hydrochloric acid + nickel metal -> hydrogen gas + aqueous nickel chloride - correct answers A.)
4Na(s) + O2(g) -> 2Na2O(s)
B.) 2NaHCO3(s) -> Na2CO3(s) + H2O(l) + CO2(g)
C.) 2HCl(aq) + Ni(s) -> H2(g) + NiCl2(aq)
law of conversion of mass - correct answers no charge is observed in the total mass of the substances
involve in the chemical change
carbon, when burned completely, forms carbon dioxide. if 11.7g of carbon combines with 31.3g of
oxygen, what mass of carbon dioxide will be produced? - correct answers 11.7g + 31.g = 43.0g
, (if something burns, it means it reacted with oxygen)
chemical equation for balancing - correct answers reactant -> products
triangle symbol - correct answers heat. supplied to the reaction; you need to add heat to make the
reaction happen
states of matter - symbols - correct answers (s) = solid state
(l) = liquid state
(g) = gas state
(aq) = dissolved in water, aqueous
T/F: matter cannot be created or destroyed - correct answers TRUUUUUUUUUUUUUU
T/F: chemical change can change the mass or the number of atoms - correct answers False! it cannot
change the mass or the number of atoms
how to balance chemical equations???? - correct answers adding coefficients to the equation
example: balance this
carbon burned in the air forms carbon monoxide gas - correct answers C(s) + O2(g) -> CO(g)
2C(s) + O2(g) -> 2CO(g)
example: balance this
hydrogen gas react with oxygen gas to produce water gas - correct answers hydrogen gas + oxygen gas -
> water gas
H2(g) + O2(g) -> H2O(g)
2H2(g) + O2(g) -> 2H2O(g)
Answers Solved Solution Guaranteed
what happens to the KE of a moving bus as it comes to stop? - correct answers it is converted into heat
an example of an endothermic process is:
A.) digestion of food
B.) burning of coal
C.) melting of ice
D.) all of the above - correct answers C
in an experiment, if the initial temperature is 72.1C and the final temperature is 26.9C, what is the
temperature change for this experiment? - correct answers -45.2C
in which of the following is energy (heat) released?
A.) evaporation of water from your skin
B.) conversion of carbon dioxide gas into dry ice (solid carbon dioxide)
C.) digestion of food
D.) all of the above
E.) only B and C - correct answers E
if 25g of iron (c=.45J/gC) and 25g of silver (c=.24J/gC), both at room temperature, are dropped into
separate glasses of 50 mL of water at 90C, which metal will reach the higher temperature? explain. -
correct answers silver
how does the amount of energy needed to heat a sample of water from 16C to 42C compare to that
needed to heat this same sample form 51C to 77C? explain. - correct answers the amount of thermal
energy (heat) is the same since the same sample (same mass and specific heat) is undergoing the same
temperature change (change in temp is 26C)
,a 280g metal bar requires 5.31kJ to change its temperature from 21C to 100C. what is the specific heat
of the metal - correct answers .24J/gC
Consider a sample of water in the gaseous state. Describe what happens to the molecules in the sample
as the sample is slowly cooled until it liquefies and then solidifies. - correct answers As water molecules
in the gas phase are cooled they begin to slow down and eventually interact strongly enough so that
they can only move around each other as the liquid state forms. Further cooling causes the molecules to
move even more slowly, eventually forming a 3-dimensional arrangement (lattice) in which each
molecule is locked into place by its strong attractions to other molecules as the liquid freezes.
What important idea is behind the practice of writing balanced chemical
equations? - correct answers Atoms are neither created nor destroyed in chemical reactions.
Convert each of the following word equations into a chemical equation and then balance it. Indicate the
physical state of each reactant and product.
A.) sodium metal + oxygen gas -> sodium oxide
B.) sodium bicarbonate -> sodium carbonate + water + carbon dioxide
C.) hydrochloric acid + nickel metal -> hydrogen gas + aqueous nickel chloride - correct answers A.)
4Na(s) + O2(g) -> 2Na2O(s)
B.) 2NaHCO3(s) -> Na2CO3(s) + H2O(l) + CO2(g)
C.) 2HCl(aq) + Ni(s) -> H2(g) + NiCl2(aq)
law of conversion of mass - correct answers no charge is observed in the total mass of the substances
involve in the chemical change
carbon, when burned completely, forms carbon dioxide. if 11.7g of carbon combines with 31.3g of
oxygen, what mass of carbon dioxide will be produced? - correct answers 11.7g + 31.g = 43.0g
, (if something burns, it means it reacted with oxygen)
chemical equation for balancing - correct answers reactant -> products
triangle symbol - correct answers heat. supplied to the reaction; you need to add heat to make the
reaction happen
states of matter - symbols - correct answers (s) = solid state
(l) = liquid state
(g) = gas state
(aq) = dissolved in water, aqueous
T/F: matter cannot be created or destroyed - correct answers TRUUUUUUUUUUUUUU
T/F: chemical change can change the mass or the number of atoms - correct answers False! it cannot
change the mass or the number of atoms
how to balance chemical equations???? - correct answers adding coefficients to the equation
example: balance this
carbon burned in the air forms carbon monoxide gas - correct answers C(s) + O2(g) -> CO(g)
2C(s) + O2(g) -> 2CO(g)
example: balance this
hydrogen gas react with oxygen gas to produce water gas - correct answers hydrogen gas + oxygen gas -
> water gas
H2(g) + O2(g) -> H2O(g)
2H2(g) + O2(g) -> 2H2O(g)
