Review for Tomorrow’s Test MolesStoichiometry Percent composition Empirical Formula

Who is this famous Italian scientist, and what does his number represent?

He is Amadeo Avogadro His number: x There are x molecules of any substance in a mole of that substance

Define what a mole is: A mole of any substance is __ _________ ______ _________ __ _____.

A mole of any substance is its molecular weight expressed in grams

How much does one mole of H 2 SO 4 weigh?

H 2 SO 4 H 2 x 1.0 = 2.0 S 1 x 32.1 = 32.1 O 4 x 16.0 = grams/mole

How many moles of NaCl are there in g ?

Number of grams/mole: Na 1 x 23.0 = 23.0 Cl 1 x 35.5 = g/mole Number of moles/ liter: g x 1 mole = 0.25 moles 58.5 g

Write a balanced equation for the formation of salt (sodium chloride) from sodium metal and chlorine gas

2 Na (s) + Cl 2 (g) 2 NaCl (s) (This is a combination or synthesis reaction)

How many grams are in 19.3 moles of AlCl 3 ?

19.3 moles x g = 2,576.6 g of AlCl 3 1 mole

How many moles are in grams of Na 2 SO 4 ?

355.3 g x 1 moles = 2.5 moles of Na 2 SO g

How many grams does x molecules of water weigh?

How many grams does x molecules of water weigh? x molecules x 1 mole x 18.0g = 54.0 g 6.02 x molecules 1 mole

How many molecules are in 112 grams of CH 4 ?

112 g x 1 mole x 6.02 x molecules = x g 1 mole molecules

Determine the percent composition of Each element in H 2 SO 4

Determine the percent composition of Each element in H 2 SO 4 H = 2 x 1.0 = 2.0 g S = 1 x 32.1 = 32.1 g O = 4 x 16.0 = 64.0 g 98.1 g/mole H = 2.0g x 100 = 2.0% 98.1g S = 32.1g x 100 = 32.7% 98.1g O = 64.0g x 100 = 65.2% 98.1g

An unknown compound is found to be 75% Carbon and 25% Hydrogen Determine it’s Empirical Formula (Use a 100 g sample )

An unknown compound is found to be 75% Carbon and 25% Hydrogen Determine it’s Empirical Formula (Use a 100 g sample ) If there is a g sample, then 75.0 g of it is C and 25.0 g of it is H Carbon: 75.0 g x 1 mole = 6.25 moles 12.0 g Hydrogen: 25.0 g x 1 mole = 25.0 moles 1.0 g Find the ratio: 6.25 = = CH 4

HCl + Na 2 CO 3  CO 2 + H 2 O + NaCl How many grams of HCl and Na 2 CO 3 would you need to make 35.1 g of salt (NaCl)? 35.1 g = 0.6 moles of NaCl. Therefore 0.6 mole of HCl and 0.3 moles of Na 2 CO 3 are needed HCl needed: 0.6 moles x 36.5 g/mole = 21.9 g Na 2 CO 3 needed: 0.3 moles x 106 g/mole = 31.8 g

Balance this equation: Al (s) + O 2 (g) Al 2 O 3 (s)

Balanced ! 4Al (s) + 3 O 2 (g) 2Al 2 O 3 (s)

__Ca + __O 2 __CaO Balance the equation and determine the Molar Ratio needed between calcium and oxygen?

2Ca + O 2 2CaO A 2 to 1 ratio between calcium & oxygen

Describe what is meant by a polyatomic ion

A group of atoms that bind together sharing an ionic charge and acting as one.

What is the sulfate radical and its valence charge?

Sulfate = SO 4 -2

What is a phosphate polyatomic ion and what is its valance charge when it forms a compound?

Phosphate = PO 4 -3