1) The number of moles present in a given mass of a substance can be found by dividing the mass in grams by the Ar or Mr. Calculate the number of moles in:

a 6 g of C

b 48 g of Mg

c 8 g of O2

d 170 g of NH3

e 45 g of H2O

f 176 g CO2.

2 Calculate the mass of:

a 20 moles of Fe

b 2 moles of H2SO4

c 0.5 moles of CO2

d 5 moles of H2O

e. 0.1 mole of Na2CO3.

3 How many atoms are there in:

a 23 g of Na?

b 12 g of Mg?

Extension

1 One mole of a substance contains the same number of atoms or molecules as one mole of any other substance.

a Which contains more atoms: 56 g of Fe or 16 g of S? Show your working.

b Which contains more molecules: 340 g of NH3 or 90 g of H2O? Show your working.

c How many more atoms are there in 48 g of C compared to 48 g of Mg? Explain your answer.

d Explain why 2 g of H2 contains more molecules than 2 g of O2.

2 Calculate which substance in the following pairs is heavier:

a 1 mole of NaCl or 1 mole of Na2CO3

b 0.5 moles of Mg or 5 moles of H2

c 10 moles of He or 1.5 moles of O2.

These questions are based on the attached photo. the experiment is about burning magnesium metal with oxygen. 1. write the balanced chemical equation for the reaction you are performing. 2. calculate the mass of magnesium metal used in each trial. o trial 1: o trial 2: 3. calculate the actual yield of magnesium oxide for each trial. o trial 1: o trial 2: 4. magnesium is the limiting reactant in this experiment. calculate the theoretical yield of mgo for each trial. o trial 1: o trial 2: 5. determine the percent yield of mgo for your experiment for each trial. o trial 1: o trial 2: 6. determine the average percent yield of mgo for the two trials. your company currently uses a process with a similar cost of materials that has an average percent yield of 91 percent. if the average percent yield of this process is higher than that, this could save the company money. what is your recommendation to the company? support your recommendation using your data, calculations, and understanding of stoichiometry gathered from this lab.

Select all of the statements which are true. electrons are located in shells or orbits around the atom. electrons orbit slowly around the atom. electrons travel in one flat path around the nucleus of an atom. the valence of an atom is determined by the number of electrons in the atom's outermost shell.

How many moles of oxygen gas are produced from the decomposition of six moles of potassium chlorate