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).
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