Chemistry, 21.08.2019 22:30 aubreyfoster

Acompound contains 69.94 percent iron and 30.06 percent oxygen. what is its molecular formula if the molar mass of the compound is 199.55 grams per mole?

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Answer from: vava19

The percentages are given in weight. You need to transform them into moles.

Take a basis of 100 grams of compound. Then there are 69.94 grams of iron and 30.06 grams of oxygen.

Use the atomic masses of iron and oxygen to obtain each number of moles.

Molar mass of iron: 55.85 g/mol
# moles of iron = 69.94 g / 55.85 g/mol = 1.252

Molar mass of oxygen: 16 g/mol
# moles of oxygen = 30.06 g / 16 g/mol =1.87875

Proportions

1.87875 moles of Oxigen/ 1.252moles of iron = 1.50 /1

3moles of Oxygen: 1 mol of Iron

Empirical formula: FeO3

Molar mass of the empirical formula: 55.85 g/mol + 3(16g/mol) = 103.85 g/mol

Molar mass of the compound / molar mass of the empirical formula = 199.55 g/mol / 103.85 g/mol = 1.92

Round to 2.

Then the molecular formula is the empirical formula times 2.

Fe2O6

Answer from: Quest

1.consider the following balanced equation and answer parts a through. show calculations for each part.

3 ag(s) + 4 hno3(aq) → 3 agno3(aq) + no(g) + 2 h2o(l)

a. calculate the number of moles of agno3 produced by the reaction of 3 moles of ag with excess hno3. if the number to the left of the compound represents the number of moles of the compound which are present, then 3 moles of ag react with 4 moles hno3 to produce 3 moles agno3 (aq).

so the answer to a would be 3 moles.

b. calculate the number of moles of agno3 produced by the reaction of 108 grams of ag with excess hno3.

i'm not sure how to plug in the grams of silver into an equation using moles to find how many moles are produced.

c. calculate the number of grams of agno3 produced by the reaction of 108 grams of ag with excess hno3

d. calculate the number of moles of no produced as a byproduct of the reaction of 108 grams of ag with excess hno3.

e. calculate the number of grams of no produced as a byproduct starting with 108 grams of ag and excess hno3.

explanation:

Answer from: Quest

$\frac{239}{94}pu+\frac{1}{0}n ====> \frac{y}{z}x+\frac{134}{54}xe+3\frac{1}{0}$

the catch is that the top numbers are atomic masses the bottom numbers are the numbers of protons and electrons in an uncharged atom. they are the number of that atoms as you would find them on the periodic table. further, the numbers on the left are used to determine the missing numbers on the right

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137 subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54 subtract 54 from both sides.

40 = z

answer

$\frac{103}{40}x=\frac{103}{40}zr$

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Acompound contains 69.94 percent iron and 30.06 percent oxygen. what is its molecular formula if the...