Advertisements
Advertisements
Question
Solve problem:
Calculate the number of moles of magnesium oxide, MgO in
- 80 g, and
- 10 g of the compound.
(Average atomic masses of Mg = 24 and O = 16)
Solution
Given: i. Mass of MgO = 80 g
ii. Mass of MgO = 10 g
To find: Number of moles of MgO
Formulae: Number of moles (n) = `"Mass of a substance"/"Molar mass of a substance"`
Calculation: i. Molecular mass of MgO = (1 × Average atomic mass of Mg) + (1 × Average atomic mass of O)
= (1 × 24 u) + (1 × 16 u)
= 40 u
∴ Molar mass of MgO = 40 g mol−1
Mass of MgO = 80 g
Number of moles (n) = `"Mass of a substance"/"Molar mass of a substance"`
= `(80 "g")/(40 "g mol"^-1)`
= 2 mol
ii. Mass of MgO = 10 g, Molar mass of MgO = 40 g mol–1
Number of moles (n) = `"Mass of a substance"/"Molar mass of a substance"`
= `(10 "g")/(40 "g mol"^-1)`
= 0.25 mol
- The number of moles in 80 g of magnesium oxide, MgO = 2 mol
- The number of moles in 10 g of magnesium oxide, MgO = 0.25 mol
APPEARS IN
RELATED QUESTIONS
The number of molecules in 22.4 cm3 of nitrogen gas at STP is ______.
Calculate the molecular mass of the following in u.
NH3
Calculate the molecular mass of the following in u.
CH3COOH
Calculate the molecular mass of the following in u.
C2H5OH
What is the ratio of molecules in 1 mole of NH3 and 1 mole of HNO3?
Solve problem:
The mass of an atom of hydrogen is 1.008 u. What is the mass of 18 atoms of hydrogen?
Solve problem:
Calculate the number of an atom of the following (Given: Atomic mass of I = 127 u).
254 u of iodine (I)
Solve problem:
Calculate the number of an atom of the following (Given: Atomic mass of I = 127 u).
254 g of iodine (I)
Solve problem:
Arjun purchased 250 g of glucose (C6H12O6) for Rs 40. Find the cost of glucose per mole.
Solve problem:
The natural isotopic abundance of 10B is 19.60% and 11B is 80.40 %. The exact isotopic masses are 10.13 and 11.009 respectively. Calculate the average atomic mass of boron
Solve problem:
Calculate the number of atoms of the following. (Average atomic mass : N = 14 u, S = 32 u)
0.4 mole of nitrogen
Solve problem:
Calculate the mass of sulfur dioxide produced by burning 16 g of sulfur in excess of oxygen in the contact process. (Average atomic mass : S = 32 u, O = 16 u)
Explain the need of the term average atomic mass.
Two 22.4 litre containers A and B contains 8 g of O2 and 8 g of SO2 respectively at 273 K and 1 atm pressure, then
Which of the following is/are true with respect to carbon-12.
Calculate the average atomic mass of naturally occurring magnesium using the following data.
| Isotope | Isotopic atomic mass | Abundance (%) |
| Mg24 | 23.99 | 78.99 |
| Mg25 | 24.99 | 10.00 |
| Mg26 | 25.98 | 11.01 |
Boron has two isotopes 10B and 11B with atomic masses 10 and 11, respectively. If its average atomic mass is 10.81, the abundance of 10B is ____________.
What is the average mass of an element if it has two isotopes, one of mass 6.015 u with 8.24 % and other of mass 7.016 u with 91.26% respectively?
One amu is equal to ________.
Calculate mass of 3.01 × 1024 atoms of an element having atomic mass 21.13.
A 100 g of sample of haemoglobin on analysis was found to contain 0.34% Fe by mass. If each haemoglobin molecule has four Fe2+ ions, the molecular mass of haemoglobin is: (Fe = 56 amu)
Which symbol replaces the unit of atomic mass, amu?
0.05 F electricity is passed through CuSO4 solution. Calculate the mass of Cu produced at cathode? (molar mass of Cu = 63.5 g mol-1)
