Chemistry
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- A. Which of the following methods can be used to seperate two compounds with different solubilities in the same solvent? a. Fractional crystallization 2
- Define Analytical chemistry. Why is accurate measurement crucial in science? The accuracy of measurement is of a great concern in analytical chemistry. This is because faulty equipment, poor data processing or human e... 2
- Why does molarity of a solution depend upon temperature ? Molarity is the number of moles of the solute present in 1 litre of the solution. Therefore, molarity depends on the volume of the solution.... 1
- Why there is a need of rounding off figures during calculation ? When performing calculations with measured quantities, the rule is that the accuracy of the final result is limited to the accuracy of the l... 1
- Define : Stoichiometry Calculations based on a balanced chemical equation are known as stoichiometric calculations 2
- Explain the following terms (a) Mole fraction (b) Molarity (c) Molality Mole fraction: It is the ratio of number of moles of a particular component of a solution to the total number of moles of the solution. If a... 1
- What do you mean by SI units ? What is the SI unit of mass ? In 1960, the general conference of weights and measures proposed revised metric system, called International system of Units i.e. SI units,... 1
- What is a limiting reagent ? Explain. Limiting reagent: i. The reactant which gets consumed and limits the amount of product formed is called the limiting reagent. ii. When a che... 1
- Explain the terms percentage composition, empirical formula and molecular formula. Percentage composition: The percentage composition of a compound is the percentage by weight of each element present in the compound. Quanti... 1
- Distinguish between accuracy and precision. Accuracy Precision Accuracy refers to nearness of the measured value to the true value. Precision refers to closeness of multiple readings o... 1
- What do you mean by significant figures? State the rules for deciding significant figures The significant figures in measurement or result are the number of digits known with certainty plus one uncertain digit. Rules for deciding... 1
- Define : Least count The smallest value that can be measured by the measuring instrument is called its least count. 2
- P. Perform each of the following calculations. Round off your answers to two digits Refer below image for detailed solution 2
- Q. Perform each of the following calculations. Round off your answers to three digits. Solution:: 5.02×10¹⁰ , 2
- R. Perform the following operations : a. 3.971 × 107 + 1.98 × 104 ; b. 1.05 × 10-4 - 9.7 × 10-5; c. 4.11 × 10-3 + 8.1×10-4; d. 2.12 × 106 - 3.5 × 105 A) 3.971 × 10⁷ + 1.98 × 10⁴ = 3.971 × 10⁷ + 0.00198 × 10⁷ = (3.971 + 0.00198) × 10⁷ = 3.97298 × 10⁷ B) 1.05 × 10⁻⁴ − 9.7 × 10⁻⁵ = 10.5 × 10⁻... 2
- A 1.000 mL sample of acetone, a common solvent used as a paint remover, was placed in a small bottle whose mass was known to be 38.0015 g. Precision: Measurement Mass of acetone observed (g) 1 38.7798-38.0015=0.7783 2 38.7795-38.0015=0.7780 3 38.7801-38.0015=0.7786 Mean= 0.7783... 2
- T. Your laboratory partner was given the task of measuring the length of a box (approx 5 in) as accurately as possible The metre stick is graduated in millimetres i.e. 1 mm to 1000 mm, and 1 mm = 0.1 cm. Therefore, if length is measured in centimetres, the le... 1
- What weight of calcium oxide will be formed on heating 19.3 g Weight of CaO formed on heating 19.3 g of CaCO₃ is 10.808 g 1
- The hourly energy requirements of an astronaut can be satisfied by the energy released when 34 grams of sucrose are “burnt” in his body. astronaut needs 916.21g of oxygen 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