Some Basic Concepts of Chemistry
Chapter 1: Some Basic Concepts of Chemistry , maharashtra state board 11th textbook
- The number of molecules in 4.4 g of CO2 is Answer: A. 6.022×10²² n=4.4/44=0.1 mol ⇒0.1×6.022×10²³ molecules. 1
- A compound contains 40% C, 6.67% H and 53.3% O by mass. Its empirical formula is Answer: D. CH2O Mole ratio C : H : O =40/12:6.67/1:53.3/16=3.33:6.67:3.33=1:2:1 . 1
- point out the difference between 12 carbon and 12 uof cardon 12 g of carbon is one mole of carbon atoms, while 12 u is the mass of a single carbon-12 atom. (Reading the question as "12 g of carbon" and... 1
- give one example of each elements Hydrogen is an example of element 1
- Distinguish between crystalline solids and amorphous solids. Crystalline solids Amorphous solids They have definite characteristic geometrical shape as constituent particles are arranged in orderly reg... 1
- 3. Give one example of each A. homogeneous mixture B. heterogeneous mixture C. element D. compound A. homogeneous mixture Ans) the molecules of constituent solute and solvent are uniformly mixed throughout its bulk. For example : Sugar and... 1
- A. What is the ratio of molecules in 1 mole of NH3 and 1 mole of HNO3 . Correct answer is 1:1 one mole of any substance,compound , or elements contain particles equal to avagadro's number i.e. 6.022 × 10²³ theref... 1
- B. Calculate number of moles of hydrogen in 0.448 litre of hydrogen gas at STP Given : volume of hydrogen at STP =0.448 L To find : number of moles of hydrogen Formula : number of moles of a gas = Volumespace of space a... 1
- C. The mass of an atom of hydrogen is 1.008 u. What is the mass of 18 atoms of hydrogen. Given : mass of hydrogen = 1.008 u To find : mass of 18 atoms of hydrogen Solution : mass of 18 atoms of hydrogen = 18 × mass of hydrogen =... 1
- D. Calculate the number of atom in each of the following (Given : Atomic mass of I = 127 u). Given : atomic mass of I=127 u A. 254 u of iodine (I) Formula : number of atoms = given space atomic space mass space of space elementover a... 1
- E. A student used a carbon pencil to write his homework. The mass of this was found to be 5 mg. With the help of this calculate. Given : mass of carbon = 5mg = 5× 10⁻³ g Atomic mass of carbon=12u Solution :: a. The number of moles of carbon in his homework writing numb... 1
- F. Arjun purchased 250 g of glucose (C6 H12O6 ) for Rs 40. Find the cost of glucose per mole Given : cost for 250 g glucose = Rs 40 , formula of glucose = C₆H₁₂O₆ To find : cost of glucose per mole solution: molecular formula of gluc... 1
- G. 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. The answer is 10.81 u Solution : Relative abundance of ¹⁰B isotope = 19.60% Relative abundance of ¹¹B isotope = 80.40% Averagespace atomic s... 2
- H. Convert the following degree Celsius temperature to degree Fahrenheit. a. 40°C b. 30° C To find : temperature in degree fahrenheit Formula : °F= 9over5(°C)+32 Solution : A. 40°C °F=9over5(°C)+32 =9over5(40)+32 =72+32=104°F B. 30... 1
- I. Calculate the number of moles and molecules of acetic acid present in 22 g of it. To find : the number of moles and molecules present in 22 g of acetic acid Solution : molecular mass of CH₃COOH =(2×atomic mass of C)+(4× at... 1
- J. 24 g of carbon reacts with some oxygen to make 88 grams of carbon dioxide. Find out how much oxygen must have been used. Given :: mass of Carbon = 24 g , mass of carbon dioxide =88g Find : mass of oxygen Solution :: beginmatrix C & +space O₂ & → CO₂\\ 24g & ? &... 1
- L. 2.0 g of a metal burnt in oxygen gave 3.2 g of its oxide. 1.42 g of the same metal heated in steam In first reaction : 3.2 g of metal oxide contains 2g metal therefore % of metal in metal oxide is 2over 3.2× 100=62.5 % and % of oxygen in m... 1
- M.In two moles of acetaldehyde (CH3 CHO) calculate the following a. Number of moles of carbon b. Number of moles of hydrogen a) Number of moles of carbon 1 molecule of CH3CHO contains 2 C-atoms. Therefore, 2 mol of CH3CHO contains 2×2 = 4 moles of Carbon. b) Number... 1
- N. Calculate the number of moles of magnesium oxide, MgO in i. 80 g and ii. 10 g of the compound. Molar mass of MgO= (atomic mass of Mg)+(atomic mass of O) =24+16 =40 g/mol 1) 80g of MgO number of mol = Given space mass over Molar space m... 1
- O. What is volume of carbon dioxide, CO2 occupying by i. 5 moles and i. 5 moles of CO_(2 )gas measured at STP. Solution :: molar volume of gas at STP is 22.4 dm³ mol⁻¹ (n)Number of moles of gas = Volumespace o... 1
- P. Calculate the mass of potassium chlorate required to liberate 6.72 dm3 of oxygen at STP beginmatrix 2KClO₃ &→ 2KCl&+3O₂\\ 2moles & & 3 moles endmatrix 2 moles of KClO₃ = 2× 122.5=245g 3 moles of O₂ =3× 22.4=67.2 dm³ hence , 245... 1
- Q. Calculate the number of atoms of hydrogen present in 5.6 g of urea, (NH2 )2 CO No of atoms of H= 2.24× 10²³ , N= 1.124× 10²³ , C= 0.562×10²³, O= 0.562× 10²³ 1
- R. Calculate the mass of sulfur dioxide produced by burning 16 g of sulfur in excess of oxygen in contact process. Answer is 32 grams 1
- Explain The need of the term average atomic mass i. Several naturally occurring elements exist as a mixture of two or more isotopes. ii. Isotopes have different atomic masses. iii. The atom... 1