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Fundamentals of Chemistry: Online Test quiz in Javascript Fundamental of Chemistry Quiz Test Exams Question of Next Good Try! You Got out of answers correct! That's TryAgain Back to Main Page

Example: Calculating the number of moles in the given number of atoms   Titanium is corrosion resistant metal that is used in rockets, aircrafts and jet engines.  Calculate the number of moles of this metal in a sample containing 3.011 x  10 23  Ti-atoms.  Tactics :                    To calculate number of moles from a given number of particles (atoms), write an equation  by placing number of moles (unknown quantity ) on right hand side and  number of atoms (known quantity) on left hand side of  the equation and follow these steps. Step 1: First write a known relation between these particles (known quantity) and mole (unknown quantity) with mole on right hand side of the equation.  6.022 × 10 23  atoms = 1 mole.  Step 2: Next, find number of moles (unknown quantity) for '1' atom of known quantity (by dividing with i.e.,  6.022 × 10 23 ...

  Self-Assessment The molecular formula of a compound used for bleaching hair is H 2 O 2.  Calculate                1. (a) Mass of this compound that would contain 2.5 moles.  (b) No. of moles of this compound that would exactly weigh 30g.  2.  A spoon of table salt, NaCl contains 12.5grams of this salt. Calculate the number of    moles it contains.  3.  before the digestive systems X-rayed, people are required to swallow suspensions      of barium sulphate BaSO4. Calculate mass of one mole of BaS O 4   Solution : Example: Calculating the number of atoms in given moles  1 . Zn is a silvery metal that is used to galvanize steel to prevent corrosion. How many atoms  are there in 1.25 moles of Zn.  2. A thin foil of aluminum (Al) is used as wrapper in food industries. How many atoms are present in a foil that contains 0.2 moles of aluminum?  Solution 1.   1 mol...

How to calculate mass, molar mass and number of moles of a substance? Molar mass calculations To calculate the molar mass of an atom, molecule, or formula unit, we need to find atomic mass, molecular or formula mass, respectively. Then express that mass into grams. Example 1.5: Calculate mass of one mole of following substances  (a) Na  (b) Nitrogen  (c) Sucrose (C 12 H 22 O 11 ) S olution:  a) Atomic mass of Na    = 23 amu      Mass of 1 mole of Na = 23g  b) Nitrogen occurs as diatomic molecules.     Molecular mass of N 2 = 14 × 2                                        = 28 amu     Mass of 1 mole of N 2  = 28 g  c) Molecular mass of C 12 H 22 O 11  = 12 × 12 + 1 × 22 + 16 × 11                                 ...

Question: What is mole? Give examples. Answer : Mole:  An amount of a substance that contains 6.022  × 10 23  particles of that substance is known as a mole of that substance.  For example, a mole of carbon has 6.022 × 10 23  atoms. A mole of sulphur has 6.022 × 10 23 atoms. A mole of water has 6.022 × 10 23  molecules.  Question: What is Avogadro’s number? Answer :  Avogadro’s number:  The number of particles present in one mole of a substance is called Avogadro's number. The experimentally determined number i.e. 6.022 × 10 23  is known as Avogadro’s number. It is represented by N A. Molar mass: The mass of one mole of substance is known as molar mass. or The mass of Avogadro’s number of particles of a substance is called molar mass. The molar mass of carbon is  12 g. The molar mass of S is 32 g.  Question: Define following terms: a. Gram atomic mass  b. Gram molecular mass  c. Gram formula mass. Answer:...

Self-Assessment Exercise 1.4: 1. Potassium Chlorate ( K Cl O 3 ) used commonly for the laboratory preparation of oxygen gas ( O 3 ). Calculate its formula mass.  2. When baking soda, Na H C O 3  is heated, carbon dioxide is released, which is responsible for the rising of cookies and bread. Determine the formula masses of baking soda and carbon dioxide.  3. Following compounds are used as fertilizers. Determine their formula masses. (i) Urea, ( N H 2 ) 2 C O (ii) Ammonium nitrate, N H4 N O 3 Solution   1. Formula mass of  K Cl O 3  = 1 × Atomic mass of K + 1 × Atomic mass of Cl + 3× Atomic mass of O                                         = 1 × 39 + 1 × 35.5 + 3 × 16                                         = 122.5 amu  2. Formula mass of  Na H C...

Question  Write the empirical formulas for the compound containing carbon to hydrogen in the following ratios: (a) 1:4 (b) 2:6 (c) 2:2 (d) 6:6  Answer:   Molecular formula from above ratio          a. C H 4        b. C 2 H 6       c. C 2 H 2           d. C 6 H 6   Empirical formula           a. C H 4        b. C H 3        c. C H               d. C H  Self-Assessment Exercise 1.3   . 1. Aspirin is used as a mild pain killer. There are nine carbon atoms, eight      hydrogen atoms and four oxygen atoms, in this compound. Write its empirical and molecular       formulas.   2. Vinegar is 5% acetic acid. It contains 2 carbon atoms, four hydrogen atoms and...

Basic Definitions: Atomic number,  Mass number,  Relative atomic mass, Atomic mass unit ,  Empirical formula and Molecular formula (Part 2) Question1.2: What are following terms: a. Atomic number  b. Mass number c. Relative atomic mass d. Atomic mass unit e. Empirical formula f. Molecular formula Answer. a. Atomic Number:   The number of protons in the nucleus of an atom is called its atomic number. For example, there is only one proton in the nucleus of H-atom; so its atomic number is one. All the atoms of an element are same and have same number of protons and hence the same atomic number. Similarly, atomic number of He is 2 amu.  b. Mass number :   The total number of protons and neutrons in the nucleus of an atom is known as its mass number. For example, mass number of C-12 is 12 (as it has six protons and six neutrons).Similarly, mass number of N-14 is 14 (because it has seven protons and seven neutrons) No. of neutrons = mass number – atomic ...

Basic Definitions| Matter, Substance, Element, Compound. Mixture, Homogeneous mixture and Heterogeneous mixture Examples (for Grade - 9 students) Question: Define following terms:  Matter Substance Element Compound Mixture Homogeneous mixture Heterogeneous mixture Answer Matter:   Matter can be anything that occupies space (volume) and has mass. Example, book, table, walls, chairs, plants, animal, etc.  Substance:   Substance is a matter that has a particular set of characteristics that differ from the characteristics of another kind of matter. For example, oxygen, water, carbon monoxide, carbon dioxide, urea, glucose, common salt etc are different substances.  Element:   A substance that cannot be converted to other simpler substances is known as an element. or A substance which has all atoms of same atomic number is called element. For example substances like oxygen, hydrogen, iron, copper, aluminum etc. are elements.  Compound:  ...

Chemistry MCQs Class IX  »