How to calculate ; 1. How many moles of the excess reagent remain after 2.0 mol

Question

How to calculate ;

1. How many moles of the excess reagent remain after 2.0 mol NaPO4 react with 2.4 mol CeCl4?

2. When a sample of CuSO4•5H2O (249.7 g/mol) is teated, it releases 180.2 grams of water. What mass of CuSO4•5H2O was originally in the sample?

3. The density of carbon tetrachloride is 1.60 g/mL-1. How many moles are there in a liter of the pure CCl4? (Molar Mass CCl4 : 154. g/mL)

4. How many moles of Sulfur dioxide can ne produced from 160g of sulfur and 320g of oxygen?

5. What mass of iron(lll) sulfide is produced from the reaction of 11.6g of iron(lll) notrate with excess sodium sulfide?
2Fe(NO3)3 (aq) + 3NaS(aq) -> Fe2S3(s)+6NaNO3(aq)

How to figure out;

1. Which molecule has the strongest bond energy?
(a) HBr (b) HF (c) HCl (d) HI

2. Which is an example of a pure comound?
(a) Water vapor (b) Argon gas (C) Air (D) Aqueous nitric acid

Explanation / Answer

1) the reaction is

4Na3P04 + 3CeCl4 ---> 12NaCl + Ce3(PO4)4

moles of CeCl4 required = ( 3/4) x moles of Na3p04

= 3 x 2 / 4

= 1.5

so

excess moles of CeCl4 = 2.4 - 1.5 = 0.9

so

0.9 moles of CeCl4 remains

2)

moles = mass / molar mass

moles of H20 = 180 / 18 = 10

given CuS04. 5H20

moles of CuS04 . 5H20 = ( 1/5) x moles of H20

moles of CuS04.5H20 = 0.2 x 10 = 2

now

mass = moles x molar mass

so

mass of CuS04 . 5H20 = 2 x 249.7 = 499.4

so

499.4 g of CuS04.5H20 is in the sample

3)

mass = density x volume

mass = 1.6 x 1000

mass = 1600 g

moles = mass / molar mass

moles = 1600 / 154

moles = 10.39

so

10.39 moles of CCl4

4)

moles of Sulphur = 160 /32 = 5

moles of oxygen = 320 / 32 = 10

S+ 02 --> S02

moles of 02 reacted = moles of S = 5

moles of 02 excess = 10-5 = 5

now

moles of S02 = moles of S reacted = 5

so

5 moles of S02 can be produced

5)

moles of Fe(N03)3 = 11.6 / 241.86 = 0.048

now

2Fe(NO3)3 (aq) + 3NaS(aq) -> Fe2S3(s)+6NaNO3(aq)

moles of Fe2S3 = 0.5 x moles of Fe(N03)3 reacted

moles of Fe2S3 = 0.5 x 0.048 = 0.024

now

mass = moles x molar mass

mass of Fe2S3 = 0.024 x 207.9 = 5

so

5 grams of Fe2S3 is produced

1) HI has the highest bond energy

2) Argon gas is pure compound , others are mixtures

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