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You need 1.50 moles of ammonia (NH3) for a reaction at STP. What volume of ammonia must you measure?

Also,

How many molecules of NaCl are in 23.40 grams NaCl?

Respuesta :

I have an idea on how to work it out, but I'll be honest I'm not that good at working these out. But have you taken a look at Bitesize? It's a really good website and should help you. Just search 'how to work out moles in chemistry' or 'moles chemistry bitesize' something like that. Hope this helps, if not come back to me :)

Answer:

1) 33.64 Liter will be volume of ammonia.

2) [tex] 2.409\times 10^{23} [/tex] molecules of NaCl are in 23.40 grams NaCl.

Explanation:

1) Using ideal gas equation:

PV = nRT

where,

P = Pressure of gas = [tex]1 atm[/tex] (at STP)

V = Volume of gas = ?

n = number of moles of gas = 1.50 mol

R = Gas constant = 0.0821 L.atm/mol.K

T = Temperature of gas = 273,15 K

Putting values in above equation, we get:

[tex]V=\frac{nRT}{P}=\frac{1.50 mol\times 0.0821 atm L/mol K\times 273.15 K}{1 atm}[/tex]

V = 33.64 L

2) [tex]N=n\times N_A[/tex]

Where:

N = Number of particles / atoms/ molecules

n = Number of moles

[tex]N_A=6.022\times 10^{23} mol^{-1}[/tex] = Avogadro's number

We have:

Molar mass of NaCl = 58.5 g/mol

n = [tex]\frac{23.40 g}{58.5 g/mol}=0.4 mol[/tex]

[tex]N=0.4 mol\times 6.022\times 10^{23} mol^{-1}=2.409\times 10^{23} molecules[/tex]

[tex] 2.409\times 10^{23} [/tex] molecules of NaCl are in 23.40 grams NaCl.