Question

multiple choice. choose the one alternative that best completes the statement or answers the question.

1. which of the below statements about global warming is false?

a) greenhouse gases allow sunlight to heat the earth.
13)
b) greenhouse gases prevent heat from leaving the earth.
c) some greenhouses gases are needed to keep the proper temperature balance.
d) if the level of greenhouse gases increases, the temperature will decrease.
e) none of the above

1. how many waffles can be made from 1 dozen eggs, assuming you have enough of all other

14)
ingredients?
given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles
a) 16
b) 12
c) 4
d) 48
e) not enough information

1. how many moles of water are made from the reaction of 2.2 moles of oxygen gas?

15)
given the reaction: 2h₂ + o₂ → 2h₂o
a) 3.3
b) 2.2
c) 4.4
d) 1.1
e) not enough information

1. how many grams of water are made from the reaction of 4.0 grams of hydrogen gas?

16)
given the reaction: 2h₂ + o₂ → 2h₂o
a) 36
b) 72
c) 18
d) 4.5
e) not enough information

1. how many grams of chlorine gas are needed to make 117 grams of sodium chloride?

17)
given the reaction: 2na + cl₂ → 2nacl
a) 142
b) 48.2
c) 71.0
d) 35.5
e) not enough information

1. iron metal reacts with oxygen to produce iron(iii) oxide. if you have 12.0 moles of iron for complete 18)

reaction, you need
a) 4.5 moles of o₂ and produce 3.0 moles of fe₂o₃.
b) 9.0 moles of o₂ and produce 6.0 moles of fe₂o₃.
c) 12.0 moles of o₂ and produce 24.0 moles of fe₂o₃.
d) 9.0 moles of o₂ and produce 3.0 moles of fe₂o₃.
e) none of the above

Explanation:

Step1: Analyze question 13

Greenhouse gases trap heat. If their level increases, temperature will increase, not decrease.

Step2: Analyze question 14

1 dozen eggs = 12 eggs. From the ratio \(2\) cups flour \(+ 3\) eggs \(+ 1\) tbs oil \(\to4\) waffles. Number of times 3 eggs are in 12 eggs: \(\frac{12}{3}=4\). Number of waffles: \(4\times4 = 16\).

Step3: Analyze question 15

From the reaction \(2H_{2}+O_{2}\to2H_{2}O\), mole ratio of \(O_{2}\) to \(H_{2}O\) is \(1:2\). For \(2.2\) moles of \(O_{2}\), moles of \(H_{2}O\): \(2.2\times2=4.4\).

Step4: Analyze question 16

Molar mass of \(H_{2}\) is \(2\space g/mol\). Moles of \(H_{2}\) in \(4.0\space g\): \(\frac{4.0}{2}=2\space mol\). From \(2H_{2}+O_{2}\to2H_{2}O\), mole ratio \(H_{2}\) to \(H_{2}O\) is \(1:1\). Moles of \(H_{2}O = 2\space mol\). Molar mass of \(H_{2}O\) is \(18\space g/mol\). Mass of \(H_{2}O\): \(2\times18 = 36\space g\).

Step5: Analyze question 17

Molar mass of \(NaCl\) is \(58.5\space g/mol\). Moles of \(NaCl\) in \(117\space g\): \(\frac{117}{58.5}=2\space mol\). From \(2Na + Cl_{2}\to2NaCl\), mole ratio \(Cl_{2}\) to \(NaCl\) is \(1:2\). Moles of \(Cl_{2}=1\space mol\). Molar mass of \(Cl_{2}\) is \(71\space g/mol\). Mass of \(Cl_{2}\): \(1\times71 = 71\space g\).

Step6: Analyze question 18

Reaction: \(4Fe+3O_{2}\to2Fe_{2}O_{3}\). Mole ratio \(Fe\) to \(O_{2}\) is \(4:3\). For \(12.0\) moles of \(Fe\), moles of \(O_{2}\): \(\frac{3}{4}\times12 = 9.0\space mol\). Mole ratio \(Fe\) to \(Fe_{2}O_{3}\) is \(2:1\). Moles of \(Fe_{2}O_{3}\): \(\frac{1}{2}\times12 = 6.0\space mol\).

Answer:

1. E. none of the above
2. A. 16
3. C. 4.4
4. A. 36
5. C. 71.0
6. B. 9.0 moles of \(O_{2}\) and produce 6.0 moles of \(Fe_{2}O_{3}\)