Solve each problem presented at each station. Show all your calculations in the

Question

Solve each problem presented at each station. Show all your calculations in the data sheet. Station 1 SiO2. How many silicon atoms are in this piece of glass? Station2 In this station, you wil find a piece of glass the size of a microscope slide. The formula for glass is Theobromine is a bitter alkaloid of the cacao plant, with the chemical formula C,H NO. It is found in chocolate. If a piece of chocolate has 1.25 x 1022 molecules of theobromine, how many grams of theobromine are in the piece of chocolate? (No physical measurement needed; just solve the calculation.) Station 3 In this station, you will find a 100 ml, graduated cylinder that contains about 35 mL of water. How many water molecules are in this graduated cylinder? (The density of water is 1.00 g/mL.) Station 4 In this station, you will find a piece of chalk with a diameter of about 1 cm and the length of about 10 cm. The formula for chalk is CaCO,. How many oxygen atoms are in this piece of chalk? Hint: Measure the mass of the chalk.

Explanation / Answer

Station 1)

A microscope slide has typical dimension of 75mm*25mm*1mm and silica(SiO2) has a density of 2.650 g/cm3

volume of the glass=75mm*25mm*1mm=1875 mm^3 =1875 mm^3 * (0.1cm)^3=1.875 cm^3 [Since,1mm^3=(0.1cm)^3]

density of SiO2= 2.650 g/cm3

mass of glass=(2.650 g/cm3)*(1.875 cm^3)=4.969 g

molar mass of SiO2=60.08g/mol

So,mol of SiO2 in the glass=4.969 g/60.08g/mol=0.0827 mol

1 mol=Avogadro's number=6.022*10^23 molecules

Number of molecules of SiO2 in the glass=0.0827 mol*(6.022*10^23 molecules/mol)=0.498*10^23 molecules

1 molecule of SiO2 has 1 atom of Si

Thus, Number of atoms of Si in the glass=0.498*10^23 atoms=4.980*10^22 atoms

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