8. how many moles are present in 34g of cu(oh)₂?(ans: 0.35 mol cu(oh)₂)\n9. how many moles are present in…

8.

Explanation:

Step1: Calculate molar mass of Cu(OH)₂

The molar mass of Cu = 63.55 g/mol, O = 16 g/mol, H = 1.01 g/mol. $M_{Cu(OH)_2}=63.55+(2\times(16 + 1.01))=63.55+(2\times17.01)=63.55 + 34.02=97.57$ g/mol

Step2: Calculate moles

Use the formula $n=\frac{m}{M}$, where $m = 34$ g and $M = 97.57$ g/mol. $n=\frac{34}{97.57}\approx0.35$ mol

Answer:

0.35 mol

9.

Explanation:

Step1: Use Avogadro's number

Avogadro's number $N_A=6.022\times 10^{23}$ molecules/mol.

Step2: Calculate moles

Use the formula $n=\frac{N}{N_A}$, where $N = 2.45\times 10^{23}$ molecules. $n=\frac{2.45\times 10^{23}}{6.022\times 10^{23}}\approx0.41$ mol

Answer:

0.41 mol

10.

Explanation:

Step1: Use Avogadro's number

Avogadro's number $N_A = 6.022\times 10^{23}$ molecules/mol. First find moles. $n=\frac{N}{N_A}=\frac{3.4\times 10^{24}}{6.022\times 10^{23}}\approx5.65$ mol

Step2: Calculate molar mass of NH₃

The molar mass of N = 14 g/mol, H = 1.01 g/mol. $M_{NH_3}=14+(3\times1.01)=14 + 3.03 = 17.03$ g/mol

Step3: Calculate mass

Use the formula $m=n\times M$. $m = 5.65\times17.03\approx96$ g

Answer:

96 g

11.

Explanation:

Step1: Calculate molar mass of Ca(NO₃)₂

The molar mass of Ca = 40.08 g/mol, N = 14 g/mol, O = 16 g/mol. $M_{Ca(NO_3)_2}=40.08+(2\times(14+(3\times16)))=40.08+(2\times(14 + 48))=40.08+(2\times62)=40.08+124 = 164.08$ g/mol

Step2: Calculate mass

Use the formula $m=n\times M$, where $n = 4.2$ mol and $M = 164.08$ g/mol. $m=4.2\times164.08\approx689$ g

Answer:

689 g

12.

Explanation:

Step1: Calculate molar mass of MgO

The molar mass of Mg = 24.31 g/mol, O = 16 g/mol. $M_{MgO}=24.31+16 = 40.31$ g/mol

Answer:

40.31 g/mol