Chemistry Chapter 9 Video Exam

According to the following balanced chemical equation, if you want to generate two moles of H2O, how many moles of O2 do you need?2 H2 + O2 → 2 H2O

1

Which is greater: 1.01 amu of hydrogen or 1.01 grams of hydrogen?

1.01 grams of hydrogen is greater than 1.01 amu of hydrogen

If it takes 20 beryllium atoms to equal the mass of two krypton atoms, what is the relative mass of beryllium compared to krypton?

1/10

If the relative mass of a pingpong ball is 1/20 that of a golf ball, how many golf balls would you need to equal the mass of 200 Ping-Pong balls?

10

Which has the greatest number of atoms?

16 g of methane, CH4

The above diagram represents a chemical reaction where the box before the arrow shows the reactants and the box after the arrow shows the products. How many diatomic molecules are represented?

2

Which equation best describes the reaction represented in the illustration above?

2 BA2 + 2 CDA3 + A2 → 2 DBA4 + 2 CA2

What is the mass of a water molecule, H2O, in grams? (1 amu = 1.661 × 10-24 g)

2.99 × 10-23 grams

How many grams of water, H2O, and propene, C3H6, can be formed from the reaction of 6.0 g of 2-propanol, C3H8O?C3H8O → C3H6 + H2O2-Propanol Propene Water

4.2 grams of propene, 1.8 grams of water

If the relative mass of a pingpong ball is 1/20 that of a golf ball, how many Ping-Pong balls would you need to equal the mass of two golf balls?

40

How many bonds between nitrogen and hydrogen are formed if you react nitrogen with hydrogen according to the following reaction?N2 + 3H2 → 2 NH3

6

Which has more atoms: 64.058 g of sulfur dioxide, SO2 (64.058 amu), or 72.922 g of hydrogen chloride, HCl (36.461 amu)?

72.922 g of HCl has more atoms than 64.058 g of SO2

How many grams of water can be formed from the reaction between 10 grams of oxygen and 1 gram of hydrogen?

9 grams of water are formed because oxygen and hydrogen react in an 8:1 ratio.

Which of the following statements about catalysts is NOT true?

A catalyst does not change the energy of the reactants or the products. Correct! All of the above are true. A catalyst alters the rate of a chemical reaction. A catalyst can be used to speed up slow reactions. A catalyst can be consumed in a reaction as long as it is regenerated.

In the laboratory, endothermic reactions are usually performed at elevated temperatures, while exothermic reactions are usually performed at lower temperatures. Why?

All of the above are true.

Are the chemical reactions that take place in a disposable battery exothermic or endothermic? Is the reaction going on in a rechargeable battery while it is recharging exothermic or endothermic?

An operating disposable battery is driven by exothermic reaction, while a recharging rechargeable battery is driven by endothermic reactions.

What is the formula mass of sulfur dioxide, SO2?

about 64 amu

The ________ is what needs to be overcome in a reaction so that it can proceed to the products.

activation energy

What is a chemical equation?

It is a shorthand notation for illustrating a chemical reaction.

If it takes energy to break bonds and you gain energy in the formation of bonds, how can some reactions be exothermic while others are endothermic?

It is the total amount of energy that matters. Sometimes some bonds are stronger than others and so you gain or lose energy when you form them.

Why is it important for a chemist to know the relative masses of atoms?

It provides information about how many atoms two samples have relative to each other

What is an endothermic reaction?

all of the above

X + Y → ZWhich of the above reactions would proceed the fastest?

c

The chlorinated fluorocarbons molecules are acting as a(n) ________ by converting hundreds of thousands of molecules before they are inactivated.

catalyst

In a chemical reaction, the bonds being formed are ________.

different from the ones broken

The following diagrams depict the reaction between gaseous chlorine, Cl2, and gaseous hydrogen, H2, to form gaseous hydrogen chloride, HCl. What should be drawn in the empty box and how many grams of products are formed?

five Cl2 molecules in empty box; 37 grams of HCl + 36 grams of Cl2

For the following balanced reaction, which of the following is a solid?2 Na(l) + Cl2(g) → 2 NaCl(s)

NaCl

Why might increasing the temperature alter the rate of a chemical reaction?

The molecules will have a higher kinetic energy and bump into one another harder.

Why does a glowing splint of wood burn only slowly in air, but rapidly in a burst of flames when placed in pure oxygen?

There is a greater number of collisions between the wood and oxygen molecules.

Why is there a drastic reduction in ozone in the spring?

There is a sudden increase in Cl atoms in the spring.

Why does iodine, I2 (s), spontaneously sublime at room temperature?

There is an increase in entropy as solid iodine, I2 (s), sublimes into iodine vapor, I2 (g), because in the gaseous phase energy is more readily dispersed.

Wild plants readily grow "all by themselves" yet the molecules of the growing plant have less entropy than the materials used to make the plant. How is it possible for a there to be this decrease in entropy for a process that occurs all by itself?

Wild plants don't grow "all by themselves." When we consider the entire system, including the sun, we find an overall increase in entropy.

Given the following generic chemical reaction, which is the reactant?X → Y

X is the reactant.

Can a catalyst react with a reactant? Why or why not?

Yes. A catalyst reacts with a reactant to form an intermediate.

Why might increasing the concentration of a set of reactants increase the rate of reaction?

You have increased the chances that any two reactant molecules will collide and react.

The atomic masses appearing in the periodic table are ________.

relative masses

What is the activation energy?

the minimum amount of energy to break the bonds in reactants

Entropy is a measure of ________.

the spreading of energy

What role do CFCs play in the catalytic destruction of ozone?

CFC molecules migrate to the upper stratosphere where they generate chlorine atoms upon being destroyed by ultraviolet light.

Which equations are balanced? a) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)b) 3Al (s) + 3 Br2 (l) → Al2Br3 (s)c) 2HgO (s) → 2 Hg (l) + O2 (g)

Equations "a" and "c" are balanced.

The reactants shown schematically below represent iron oxide, Fe2O3 and carbon monoxide, CO. Which of the following is the correct full balanced chemical equation for what is depicted?

Fe2O3 + 3 CO → 2 Fe + 3 CO2

Does the ozone pollution from automobiles help alleviate the ozone hole over the South Pole?

No, because the ozone decomposes before reaching the upper atmosphere.

Explain the connection between photosynthetic life on the earth and the ozone layer.

Photosynthetic plants produce the oxygen from which the ozone layer forms.

How is Avogadro's number related to the numbers on the periodic table?

The atomic mass listed is the mass of Avogadro's number's worth of atoms.

A friend argues that if mass were really conserved he would never need to refill his gas tank. What explanation do you offer your friend?

The atoms (mass) of gasoline are converted into exhaust fumes.

What happens to the entropy of a system as the components of the system are introduced to a larger number of possible arrangements, such as when liquid water transforms into water vapor?

The entropy increases because there are more ways in which the energy can disperse.