3Si + 2N2 --> Si3N4 (as given)

n(Si) = m/MM = 38.25/28.085 = 1.3619 mol
n(N2) = 14.33/2*14.007 = 0.5115 mol

Therefore, N2 is limiting and Si is in excess
The molar ratio of 2N2:Si3N4 is 2:1
So, 0.0575 mol of silicon nitride is formed (dividing 0.5115 by 2)

m of silicon nitride= n*mm = 0.0575*140.283 = 8.06627... g
= 8.066g (4 significant figures)

(hopefully it is right, but double check in case i did something wrong) :)

6 0

3 years ago

Hydrogen gas is filled in a 224 ml glass container at 0 degree celcius and 1 atmospheric pressure. What are the number of molecu

Step2247 [10]

Answer:

$\boxed{\text{6.02 $\math{\times 10^{21}}$ molecules}}$

Explanation:

A pressure of 1 atm and a temperature of 0 °C is the old definition of STP. Under these conditions, 1 mol of a gas occupies 22.4 L.

1. Calculate the moles of hydrogen.

$n = \text{0.224 L} \times \dfrac{\text{1 mol}}{\text{22.4 L}} = \text{0.0100 mol}$

2. Calculate the number of molecules

$\text{No. of molecules} = \text{0.0100 mol} \times \dfrac{\text{6.022 $\times 10^{23}$ molecules}}{\text{1 mol}}\\\\= \textbf{6.02 $\mathbf{\times 10^{21}}$ molecules}\\\\\text{The sample contains }\boxed{\textbf{6.02 $\mathbf{\times 10^{21}}$ molecules}}$

8 0

3 years ago

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The concentration of pb2+ in a solution saturated with pbbr2(s) is 2.14 ✕ 10-2 m. calculate ksp for pbbr2.

Ugo [173]

Concentration = 2.14 âś• 10-2 m
For [Br-], there are 2 ions so 2 x 2.14 x 10^-2 =4.28 x 10^-2
Ksp = [Pb][Br]^2 = 2.14 âś• 10-2 x (4.28 x 10^-2 )^2 = 39.20 x 10^-6
Ksp = 3.92 x 10^-5

3 0

3 years ago

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