Chemistry Homework Help ??!! Desperate .?

1) How many grams of oxygen gas are contained in 30.0 L of oxygen gas at STP? (standard time and pressure)

2) What volume at STP will 0.50 mol of ammonia gas have?

3) 0.0032 grams of nicotine (F.M.= 162 g/mol) are contained in 1 cigarette. How many molecules is this?

4) What volume will 325 grams of sulfur dioxide occupy at STP? What is the density of this gas?

5) 3.00 grams of dry ice (solid carbon dioxide) is converted to a gas. How many moles are present of this gas? What volume will it occupy?

Please show work.

1 Answer

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  • 8 years ago
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    STP means Standard Temperature and Pressure ... [so T = 0° C and P = 1 atm]

    At STP 1 mole of gas occupies 22.4 L

    1) molar mass O2 = 16.00 x 2 = 32.00 g/mol

    so mass O2 = 30.0 L O2 x [1 mol / 22.4 L] x [32.00 g / mol] = 42.9 g O2 (to 3 sig figs)

    2) volume of NH3 = 0.50 mol NH3 x [22.4 L / mol] = 11 L NH3 (to 2 sig figs)

    3) A mole of any compound has 6.022 x 10²³ molecules

    so number of molecules of nicotine = 0.0032 g nicotine x [1 mol / 162 g] x [6.022 x 10²³ molecules / mol]

    = 1.2 x 10¹⁹ molecules of nicotine (to 2 sig figs)

    4) molar mass SO2 = 32.07 + 16.00 x 2 = 64.07 g/mol

    volume of SO2 = 325 g SO2 x [1 mol / 64.07 g] x [22.4 L / mol] = 114 L (to 3 sig figs)

    density = mass / volume

    so density SO2 = 325 g / 114 L = 2.85 g/L (to 3 sig figs)

    5) molar mass CO2 = 12.01 + 16.00 x 2 = 44.01 g/mol

    mol CO2 = 3.00 g CO2 x [1 mol / 44.01g] = 0.0682 mol CO2 (to 3 sig figs)

    volume occupied = 0.0682 mol CO2 x [22.4 L / mol] = 1.53 L CO2 (to 3 sig figs) (assuming STP)

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