Chemistry
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- 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
- Explain Molar mass. The mass of one mole of a substance (element/compound) in grams is called its molar mass. The molar mass of any element in grams is numerica... 1
- Explain Mole concept. Even a small amount of any substance contains very large number of atoms or molecules. Therefore, a quantitative adjective 'mole' is used to... 1
- Explain Formula mass with an example. The formula mass of a molecule (also known as formula weight) is the sum of the atomic weights of the atoms in the empirical formula of the... 1
- Explain : Molar volume of gas. One mole of any gas occupies a volume of 22.4 dm³ at standard temperature (0^o C) and pressure (1 atm) (STP). The volume of 22.4 dm3 at STP... 1
- F. Types of matter (on the basis of chemical composition). On the basis of composition, matter can be classified as compound, element and mixture. Solids, liquids and gases are physical states of mat... 2
- State the law of multiple proportions When two elements A and B form more than one compounds, the masses of element B that combine with a given mass of A are always in the ratio... 1
- State and explain the law of conservation of mass 'mass can neither be created nor destroyed' this law is know as law of conservation of mass . Antoine Lavoisier carefully performed many com... 1
- What is meant by molar volume of a gas ? One mole of any gas occupies a volume of 22.4 dm3 at standard temperature (0^o C) and pressure (1 atm) (STP). The volume of 22.4 dm³ at STP... 1
- What is the SI unit of amount of a substance ? Answer: The SI unit of amount of substance is the mole (symbol: mol). The mole is one of the seven SI base units. One mole is the amount of... 1
- How many particles are present in 1 mole of a substance ? The number of particles present in 1 mole is 6.022 × 10²³ It is Avogadro's number equal to 6.022×10²³ and is expressed as the symbol N_A. 1