29. An experiment was carried out to find the Mr of vitamin C (ascorbic acid). It was found that 1 g contains 0.00568 moles of Vitamin C molecules. Calculate the Mr of vitamin C.

30. How many atoms are in 50 moles of atoms?

31. How many molecules are in 20 moles of F2?

32. How many atoms are in 20 moles of F2?

33. How many electrons are in 20 moles of F2?

34. How many atoms are in 34 moles of Na?

35. How many atoms are in 450 g of Ti?

36. What is the Mr of a substance if 3.8 moles of it has a mass of 591 g?

37. Challenge: a student has 3.6722x1024 atoms of an element, and it has a mass of 237.9 g. What is the element?

1 answer

Let's solve each question step by step:

29. Calculate the Mr of vitamin C (ascorbic acid).

Given:

  • Mass of vitamin C = 1 g
  • Moles of vitamin C = 0.00568 moles

To find the molar mass (Mr): \[ \text{Mr} = \frac{\text{mass}}{\text{moles}} = \frac{1 , \text{g}}{0.00568 , \text{moles}} \approx 176.76 , \text{g/mol} \]

30. How many atoms are in 50 moles of atoms?

Using Avogadro's number (\(6.022 \times 10^{23}\) atoms/mole): \[ \text{Number of atoms} = 50 , \text{moles} \times 6.022 \times 10^{23} , \text{atoms/mole} \] \[ \approx 3.011 \times 10^{25} , \text{atoms} \]

31. How many molecules are in 20 moles of F2?

Using Avogadro's number: \[ \text{Number of molecules} = 20 , \text{moles} \times 6.022 \times 10^{23} , \text{molecules/mole} \] \[ \approx 1.2044 \times 10^{25} , \text{molecules} \]

32. How many atoms are in 20 moles of F2?

Since each F2 molecule contains 2 fluorine atoms: \[ \text{Number of atoms} = 20 , \text{moles of F2} \times 6.022 \times 10^{23} , \text{molecules/mole} \times 2 , \text{atoms/molecule} \] \[ \approx 2.4088 \times 10^{25} , \text{atoms} \]

33. How many electrons are in 20 moles of F2?

Each F2 molecule has 2 fluorine atoms, and each atom has 9 electrons (as fluorine has an atomic number of 9): \[ \text{Number of electrons} = 20 , \text{moles of F2} \times 6.022 \times 10^{23} , \text{molecules/mole} \times 2 , \text{atoms/molecule} \times 9 , \text{electrons/atom} \] \[ \approx 4.32792 \times 10^{26} , \text{electrons} \]

34. How many atoms are in 34 moles of Na?

Using Avogadro's number: \[ \text{Number of atoms} = 34 , \text{moles} \times 6.022 \times 10^{23} , \text{atoms/mole} \] \[ \approx 2.046 \times 10^{25} , \text{atoms} \]

35. How many atoms are in 450 g of Ti?

First, find the molar mass of titanium (Ti), which is approximately 47.87 g/mol. Now, calculate the number of moles in 450 g of Ti: \[ \text{Moles of Ti} = \frac{450 , \text{g}}{47.87 , \text{g/mol}} \approx 9.4 , \text{moles} \] Thus, calculate the number of atoms: \[ \text{Number of atoms} = 9.4 , \text{moles} \times 6.022 \times 10^{23} , \text{atoms/mole} \] \[ \approx 5.65 \times 10^{24} , \text{atoms} \]

36. What is the Mr of a substance if 3.8 moles of it has a mass of 591 g?

To find the molar mass (Mr): \[ \text{Mr} = \frac{\text{mass}}{\text{moles}} = \frac{591 , \text{g}}{3.8 , \text{moles}} \approx 155.0 , \text{g/mol} \]

37. Challenge: a student has \(3.6722 \times 10^{24}\) atoms of an element, and it has a mass of 237.9 g. What is the element?

First, calculate the number of moles of the element using Avogadro's number: \[ \text{Moles} = \frac{3.6722 \times 10^{24} \text{ atoms}}{6.022 \times 10^{23} \text{ atoms/mole}} \approx 6.09 , \text{moles} \]

Next, find the molar mass (Mr): \[ \text{Mr} = \frac{237.9 , \text{g}}{6.09 , \text{moles}} \approx 39.06 , \text{g/mol} \]

The element with an approximate molar mass of 39.06 g/mol is potassium (K).