Question

. 1. Calculate the number of moles of magnesium presentin a magnesium ribbon weigng 12 g. Molar atomic mass of magnesium is 24g/ mol
2. Verify by calculating that
(a) 5 moles of CO2 and 5 moles of H2O do not have the same mass.
(b) 240 g of calcium and 240 g magnesium elements have a mole ratio of 3:5.
3. Find theratio by mass of the combining elements in the following compounds.
(a) CaCO3 (b) MgCl2 (c) H2SO4 (d) C2H5OH (e) NH3 (f) Ca(OH)2
4. Calcium chloridewhen dissolved in water dissociates intoits ions according to the following equation.
CaCl2 (aq) → Ca2+ (aq) + 2Cl– (aq)
Calculate the number of ions obtained from CaCl2 when 222 g of it is dissolvedin water.
5. The difference in the mass of 100 moles each of sodium atoms and sodium ions is 5.48002 g. Compute the mass of an electron.
6. Cinnabar (HgS) is a prominentore of mercury. How many grams of mercury are present in 225 g of pure HgS? Molar mass of Hg and S are 200.6 g /mol and 32 g/ mol respectively.
7. The mass of one steel screw is 4.11g. Find the mass of one mole of these steel screws. Compare ts value with themass of the Earth (5.98 × 1024kg). Wch one of the two is heavier and by how many times?
8. A sample of vitamin C is known to contain 2.58 ×1024 oxygen atoms. How many moles of oxygen atoms are present in the sample?
9. Compute the difference in masses of 103 moles each of magnesium atoms and magnesium ions. (Mass of an electron = 9.1×10–31 kg)
10. Compute the number of ions present in 5.85 g of sodium chloride.
11. A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present in one gram of ts sampleof gold?
12. Compute the difference in masses of one mole each of aluminium atoms and one mole of its ions. (Mass of an electron is 9.1×10–28 g). Wch one is heavier?
13. A silver ornament of mass ‘m’ gram is polished with goldequivalent to 1% of the mass of silver. Compute the ratio of the number of atoms of gold and silverin the ornament.
14. A sample of ethane (C2H6) gas has the same mass as 1.5 ×1020 molecules of methane (CH4). How many C2H 6 molecules does the sample of gas contain?
15. Fillin the blanks
(a) In a chemical reaction, the sum of the masses of the reactants and productsremains unchanged. Ts is called ————.
(b) A group of atoms carrying a fixed charge on them is called ————.
(c) The formula unit massof Ca3 (PO4)2 is ————.
(d) Formula of sodium carbonate is ———— and that of ammonium sulphate is ————.

Answer 1

plz see the picture uploaded

Answer 2

Answer:

Explanation:

We know that one mole of an element weighs equal to its gram atomic mass. Thus, for any given amount of an element number of corresponding moles can be found using unitary method. From the above information, $\frac{{12}}{{24}} = 0.5$ moles of magnesium are present in magnesium ribbon.