MOLES - NM Chemistry



MOLES

We measure ________________ in grams. We measure volume in __________________. We count pieces in _________________. The number of moles is defined as the number of __________________ atoms in exactly ____ grams of carbon-12. ____ mole is 6.022 x 1023 particles. 6.022 x 1023 is called __________________ number. Representative particles are the smallest pieces of a substance. For a molecular compound it is a(n) ______________________. For an ionic compound it is a ______________________ ______________. For an element it is a(n) ________________.

How many oxygen atoms are in the following?

a) CaCO3 b) Al2(SO4)3

How many total ions are in the following?

a) CaCl2 b) NaF c) Al2S3

MOLE CONVERSIONS

1. How many atoms of carbon are there in 1.23 moles of carbon?

2. How many molecules of CO2 are in 4.56 moles of CO2?

3. How many atoms of iron are in 0.600 moles of iron?

4. How many moles are in 7.78 x 1024 formula units of MgCl2?

5. How many moles of water are 5.87 x 1022 molecules of water?

6. How many moles of aluminum are 1.2 x 1024 atoms of aluminum?

Calculate the number of particles (atoms, ions or molecules) in each of the following.

a) 3.4 moles Na2S b) 0.0020 moles Zn

c) 1.77 x 10-11 moles C d) 92.35 moles O2

Calculate the number of moles in each of the following.

a) 3.4 x 1024 molecules HCl b) 8.7 x 1021 atoms Zn

c) 1.77 x 1018 ions Al+3 d) 2.66 x 1026 atoms Cu

MOLAR MASS

Molar mass is the generic term for the mass of one _____________. It may also be referred to as gram molecular mass, gram formula mass, and gram atomic mass. The unit is ______________. To determine the molar mass of an element, find the element’s symbol on the periodic table and round the mass so there is __________ digit beyond the decimal.

Calculate the molar mass of the each of the following elements.

a) sulfur (S) b) chromium (Cr) c) bromine (Br)

To determine the molar mass of a compound, find the mass of all elements in the compound.

If necessary, ___________________ an element’s mass by the subscript appearing beside that element in the compound’s formula (or ________________ of the subscripts).

Calculate the molar mass of each of the following compounds.

a) Na2S b) N2O4 c) C6H12O6 d) Ca(NO3)2

MASS-PARTICLE/MOLE CONVERSIONS

1. How many atoms of lithium are in 1.00 g of Li?

2. How many molecules of sodium oxide are in 42.0 g of Na2O?

3. How much would 3.45 x 1022 atoms of uranium (U) weigh?

4. How many moles of magnesium are in 56.3 g of Mg?

5. How many moles is 5.69 g of NaOH?

6. How many grams of sodium chloride are in 3.45 moles of NaCl?

7. How many moles is 4.8 g of CO2?

8. How many grams is 9.87 moles of H2O?

9. How many molecules are in 6.8 g of CH4?

10. How much does 49.0 molecules of C6H12O6 weigh?

GASES

Many of the chemicals we deal with are gases. They are difficult to weigh, and we need to know how many moles of gas we have. Two things affect the volume of a gas: temperature and pressure. Standard temperature is ______ ºC, and standard pressure is ______ atm. Standard temperature and pressure is abbreviated STP. At STP 1 mole of gas occupies ______ L. 22.4 L is called the _____________ volume. Avogadro’s Hypothesis - At the same temperature and pressure equal volumes of gas have the same number of _______________________.

GAS CONVERSIONS

1. What is the volume of 4.59 mole of CO2 gas at STP?

2. How many moles is 5.67 L of O2 at STP?

3. What is the volume of 8.8 g of CH4 gas at STP?

4. How many grams is 16.2 L of O2 at STP?

Calculate the number of liters in each of the following.

a) 3.10 x 1024 molecules Cl2 b) 8.7 moles Ne

c) 2.77 x 1018 atoms He d) 266 grams SO2

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