PLS HELP - CHEM - STOICHIOMETRY HWWW?

[匿名]

2016-05-30 6:21 pm

I am rly struggling with chemistry this year, I have a few hw problems that I rly dont get at all

1.) How many molecules are in 1 L of chlorine gas at STP?

2.) If we needed 0.5 moles of acetic acid, how many grams are needed>

3.) How many grams of iron (III) chloride will be needed to make 100 mL of a 0.02 M solution?

I would GREATLYYY appreciate if u showed ur workings as well if u get it...I rly wanna know how to do this and I am provided to show my workings as well.

Thanks ;)

回答 (1)

fooks

2016-05-30 6:53 pm

1)
1 mole of chlorine gas occupies a volume of 22.4 L at STP.
Number of moles of chlorine gas = (1 L) / (22.4 L/mol) = 1/22.4 mol

1 mole of chlorine gas contains 6.022 × 10²³ chlorine molecules.
Number of chlorine molecules = (6.022 × 10²³ /mol) × (1/22.4 mol) = 2.69 × 10²²

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2)
The chemical formula of acetic acid is CH₃COOH.
Molar mass of CH₃COOH = (12.01×2 + 1.008×4 + 16.00×2) g/mol = 60.05 g/mol
Number of moles of CH₃COOH = (60.05 g/mol) × (0.5 mol) = 30.0 g

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3)
No. of moles of FeCl₃ = (0.02 mol/L) × (100/1000 L) = 0.002 mol
Molar mass of FeCl₃ = (55.85 + 35.45×3) g/mol = 162.2 g/mol
Mass of FeCl₂ = (162.2 g/mol) × (0.002 mol) = 0.324 g

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