Question 1(multiple choice worth 4 points)
(05.04 mc)

what mass of co is needed to react completely with 55.0 g of fe2o3 in the reaction: fe2o3(s) + co(g) → fe(s) + co2(g)?

4.82 g co
9.64 g co
14.5 g co
28.9 g co
question 2(multiple choice worth 4 points)
(05.04 lc)

which of the following is a valid mole ratio from the balanced equation 2c3h6 + 9o2 → 6co2 + 6h2o?

one mole of c three h six over two moles of c o two
six moles of h two o over nine moles of o two
two moles of c three h six over six moles of o two
three moles of h two o over 2 moles of c o two
question 3(multiple choice worth 4 points)
(05.04 mc)

read the following chemical equation.

fe + o2 → fe2o3

which of the following fractions can be used for the mole ratio to determine the mass of fe from a known mass of fe2o3?

four over two
three over two
two over three
two over four
question 4(multiple choice worth 4 points)
(05.04 mc)

in an experiment, zinc chlorate decomposed according to the following chemical equation.

zn(clo3)2 → zncl2 + o2

(molar mass of zn(clo3)2 = 232.29 g/mol; zncl2 = 136.286 g/mol; o2 = 31.998 g/mol)

if the mass of zinc chlorate was 150 grams, which of the following calculations can be used to determine the mass of oxygen gas formed?

(150 × 1 × 232.29) ÷ (31.998 × 3) grams
(150 × 3 × 232.29) ÷ (31.998 × 1) grams
(150 × 1 × 31.998) ÷ (232.29 × 3) grams
(150 × 3 × 31.998) ÷ (232.29 × 1) grams
question 5(multiple choice worth 4 points)
(05.04 lc)

how many moles of sodium cyanide (nacn) would be needed to produce 4.2 moles of sodium sulfate (na2so4)?

h2so4 + 2nacn → 2hcn + na2so4

2.1 mol nacn
4.2 mol nacn
8.4 mol nacn
12.0 mol nacn

Answer

Answer 1 : 28.9 g of CO is needed.

Answer 2 : Six moles of over Nine moles of

Answer 3 : Four over two fraction can be used for the mole ratio to determine the mass of Fe from a known mass of .

Answer 4 : Mass of = (150 × 3 × 31.998) ÷ (232.29 × 1) grams

Answer 5 : 8.4 moles of sodium cyanide (NaCN) would be needed.

Solution

Solution 1 : Given,

Given mass of = 55 g

Molar mass of = 159.69 g/mole

Molar mass of CO = 28.01 g/mole

Moles of = = = 0.344 moles

Balanced chemical reaction is,

From the given reaction, we conclude that

1 mole of gives              →         3 moles of CO

0.344 moles of gives    →         3 × 0.344 moles of CO

                                                     =         1.032 moles

Mass of CO = Number of moles of CO × Molar mass of CO

                    = 1.032 × 28.01

                    = 28.90 g

Solution 2 : The balanced chemical reaction is,

From the given reaction, we conclude that the Six moles of over Nine moles of is the correct option.

Solution 3 : The balanced chemical reaction is,

From the given balanced reaction, we conclude that Four over two fraction can be used for the mole ratio to determine the mass of Fe from a known mass of .

Solution 4 : Given,

Given mass of = 150 g

Molar mass of = 232.29 g/mole

Molar mass of = 31.998 g/mole

Moles of = =

The balanced chemical equation is,

From the given balanced equation, we conclude that

1 mole of gives          →       3 moles of

of gives  →   of

Mass of = Number of moles of × Molar mass of   =

Therefore, the mass of = (150 × 3 × 31.998) ÷ (232.29 × 1) grams

Solution 5 : Given,

Number of moles of = 4.2 moles

Balanced chemical equation is,

From the given chemical reaction, we conclude that

1 mole of obtained from 2 moles of NaCN

4.2 moles of obtained   →   2 × 4.2 moles of NaCN

Therefore,

The moles of NaCN needed = 2 × 4.2 = 8.4 moles

The number of moles is obtained by dividing the mass by the molar mass.

1) The reaction equation is;

Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g)

Number of moles of Fe2O3  reacted =  55.0 g/160 g/mol =0.34

From the balanced reaction equation;

1 moles of Fe2O3 reacts with 3 moles of CO

0.34 moles of Fe2O3 reacts with  0.34 moles × 3 moles/1 moles

= 1.02 moles of CO

Mass of CO =  1.02 moles × 28 g/mol = 28.9 g CO

2)  Looking at the balanced chemical reaction equation as shown in the question, the valid mole ratio is six moles of H two O over nine moles of O two.

3) The balanced reaction equation is; 4 Fe +3 O2 → 2Fe2O3. From this we can see that the mole ratio to determine the mass of Fe from a known mass of Fe2O3 is four over two.

4) Given that the balanced reaction equation is; Zn(ClO3)2 = ZnCl2 + 3 O2

The equation that could be used to calculate the mass of oxygen formed is;

(150 × 3 × 31.998) ÷ (232.29 × 1) grams

5) The balanced reaction equation is; H2SO4 + 2NaCN = 2HCN + Na2SO4

From the reaction equation;

2 moles of NaCN  yields 1 mole of Na2SO4

4.2 moles of NaCN  yields 4.2 moles ×  1 mole /2 moles

= 2.1 mol NaCN

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c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.