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.

1. an experiment in your science class lists the materials needed for the lab. it is your job, as a lab partner, to measure out 25 ml of distilled water and 2.5 grams of magnesium. what lab measuring tools would you choose to measure each substance and how would you use each tool to get the correct amounts? be sure to describe the process you would follow step-by-step. (5 points) 2.which of the following is an si base unit for measuring mass? (2 points) ampere gram meter pound 3.which of the following is an si base unit for time? (2 points) decades hours minutes seconds 4.which of the following tools should a scientist use to measure an object in milligrams? (2 points) graduated cylinder pan balance tape measure thermometer 4.which of the following tools should a scientist use to measure an object in milligrams? (2 points) graduated cylinder pan balance tape measure thermometer. 5.a pencil beside a metric ruler. the ruler is scaled from 1 centimeter to 10 centimeters, with markings for millimeters between each number. one end of the pencil is beside the 0 on the ruler, and the pencil point is beside the 5. which of the following measurements is accurate but not precise? (2 points) 5 mm 5 cm 50 mm 50 cm 6. which of the following prefixes represents the largest value? (2 points) giga hector kilo milli 7. which of the following types of graphs is best for plotting the percentages of a whole value in a data set? (2 points) bar graph circle graph histogram line graph