Question

Calculate the number of moles

9.86 g strontium hydroxide

34.2 kg lead(II) sulfate

5.39 g N₂O₄

2.05 mg NaAuCl₄

Calculate mass in grams :

0.755 mol zinc chloride

0.203 μmol potassium chlorate

0.424 mmol POCl₃

4.32 × 10^-3 mol (NH₄)₂HPO₄

0.789 mol S

3.99 mol N

4.86 mol Al

Answer 1

1)

Molar mass of Sr(OH)2,

MM = 1*MM(Sr) + 2*MM(O) + 2*MM(H)

= 1*87.62 + 2*16.0 + 2*1.008

= 121.636 g/mol

mass(Sr(OH)2)= 9.86 g

number of mol of Sr(OH)2,

n = mass of Sr(OH)2/molar mass of Sr(OH)2

=(9.86 g)/(121.636 g/mol)

= 0.0811 mol

Answer: 0.0811 mol

2)

Molar mass of PbSO4,

MM = 1*MM(Pb) + 1*MM(S) + 4*MM(O)

= 1*207.2 + 1*32.07 + 4*16.0

= 303.27 g/mol

mass(PbSO4)= 34.2 kg

= 34200.0 g

number of mol of PbSO4,

n = mass of PbSO4/molar mass of PbSO4

=(34200.0 g)/(303.27 g/mol)

= 113 mol

Answer: 113 mol

3)

Molar mass of N2O4,

MM = 2*MM(N) + 4*MM(O)

= 2*14.01 + 4*16.0

= 92.02 g/mol

mass(N2O4)= 5.39 g

number of mol of N2O4,

n = mass of N2O4/molar mass of N2O4

=(5.39 g)/(92.02 g/mol)

= 0.0586 mol

Answer: 0.0586 mol

4)

Molar mass of NaAuCl4,

MM = 1*MM(Na) + 1*MM(Au) + 4*MM(Cl)

= 1*22.99 + 1*197.0 + 4*35.45

= 361.79 g/mol

mass(NaAuCl4)= 2.05 mg

= 2.05*10^-3 g

number of mol of NaAuCl4,

n = mass of NaAuCl4/molar mass of NaAuCl4

=(2.05*10^-3 g)/(361.79 g/mol)

= 5.67*10^-6 mol

Answer: 5.67*10^-6 mol

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