stoichiometry review - PreDP

Moles

100

How many moles of Cl atoms are in 2 moles of Cl₂ ?

4 moles of Cl atoms

200

How many moles of oxygen atoms are in 0.5 moles of H₂O₂?

1 mole of oxygen atoms

2*0.5=1

300

How many moles of gold are in a ring that weighs 1g?

n=1/196.97=0.005 mol

m=nxM

400

There are 240 g of water (H₂O) in a glass. How many moles is it?

240/18=13.3 moles of water

500

How many moles are in 49 g of H₂SO₄?

0.5 mole H₂SO₄

Mass

100

What is the molar mass of CaCO₃?

_{100 g/mol}

200

What is the mass of 0.1 mole of C₆H₁₂O₆?

180*0.1=18g

300

The mass of 0.2 moles of a substance is 8.8g. What is the molar mass of the substance?

44 grams

400

The mass of 1 mole of X₂O₃ is 160 g. what is the molar mass of X?

56 grams

(160-3*16)/2=56

500

A sample of 7g consists of 0.25 moles of a diatomic molecules (X₂) of an element. What is its molar mass of X?

14g (N)

since the molecules are diatomic, they consist of 0.5 moles of the element

0.5 mole------7g

1 mole-----Xg    >>7/0.5=14

Chemical equations

100

How many moles of HCl will be produced from 10 moles of H₂?        H₂ + Cl₂ --> 2HCl

20 moles HCl

200

How many moles of S₈ are required to produce 16 mole FeS?     8Fe + S₈ ---> 8FeS

2 moles of S₈

300

Balance the reaction: ___H₂+___N₂ -->___NH₃

3H₂ + N₂ --> 2NH₃

400

How many moles of O₂ are required to react with 10 moles of Fe in the reaction: 4Fe+3O₂-->2Fe₂O₃

7.5 moles of O₂

500

How many moles of O₂ will react with 2 moles of C₂H₄ in the unbalanced reaction C₂H₄+O₂-->CO₂+H₂O

6 moles of O₂

C₂H₄+3O₂-->2CO₂+2H₂O

Reaction calculations

100

In the reaction 2Fe+3Cl₂-->2FeCl₃. What is the mass of iron (Fe) that is needed to produce 2 moles FeCl₃?

2x55.85=111.7 g Fe

200

In the reaction 2Fe+3Cl₂-->2FeCl₃. What is the mass of chlorine (Cl₂) that is needed to produce 4 moles FeCl₃?

6 moles of Cl₂  which are 6x70.9=425.4g

300

what is the mass of oxygen thats required to burn 46g of C₂H₅OH?   C₂H₅OH + 3O₂ --> 2CO₂ + 3H₂O

96g of O₂

400

Determine the mass of ethanol (C₂H₅OH) that burned when 540g of water were produced. C₂H₅OH + 3O₂ --> 2CO₂ + 3H₂O

460g ethanol was burned

540g water are 540/18=30 moles of water.

we need 10 moles of C₂H₅OH.

500

What mass of iron is needed to react with 16.0 grams of sulfur?    8 Fe + S₈ ---> 8 FeS

27.9 g Fe

M(S₈)=256g/mol

m(S₈)= 16g

m=nxM

16=nx256

n=0.0625 mol

We need 8x0.0625=0.5 mole of iron

which are 0.5x55.85=27.9 g Fe