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Chemistry Questions and Answers August 19, 2020

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How many oxygen atoms are in 2.48 g of Na2S2O3.5H2O? A. 6.02 x1021 B. 1.81x1022 C. 4.82x1022 D. 3.01x1022

Which of the following contains the greatest number of oxygen atoms A. 0.200 mol CO2 B. 0.300 mol P4O6 C. 0.400 mol SO3 D. 0.500 mol H2O

Which of the following contains the greatest number of atoms A. 1.0 g H2(g) B. 4.4 g CO2(g) C. 3.2 g SO2(g) D. 5.0 g Ne(g)

10.0 g of which of the following contains the greatest number of molecules A. CO2(g) B. NO(g) C. CH4(g) D. N2(g)

Which of the following contains the same number of atoms as in 24.08 g CH4? A. 3.5 mol O2 B. 0.5 mol O3 C. 2.5 mol CO2 D. 1.5 mol Ar

100 g of which of the following contains the greatest number of atoms A. Ar(g) B. Cl2(g) C. P4(g) D. S8(g)

1.0 dm3 of which of the following contains the greatest number of atoms A. He(g) B. CO2(g) C. H2(g) D. CH4(g)

Convert each of the following from the number of molecules to moles (mol). Please provide the appropriate number of significant figures for your answer.,a) 1.45 x 1022 Bi(NO3)3 molecules,b) 2.2 x 1024 KCO3 molecules,c) 9.1 x 1023 Sb2S3 molecules,d) 8.1 x 10 CIO4 molecules

Convert each of the following from moles (mol) to number of molecules. Please provide the appropriate number of significant figures for your answer.,a) 1.8 mol Ba3(PO4)2,b) 0.10 mol KCO3,c) 0.2900 mol NH4,f) 0.003 mol CuCNS,g) 1.00 mol Bi(NO3)3

Without doing any calculations, predict whether the number of moles will be greater or less than 1 for each number of molecules given below.,a) 2.2 x 1024 molecules,b) 2.2 x 1023 molecules,c) 8.96 x 1023 molecules

Without doing any calculations, predict whether the number of molecules will be greater or less than Avogadros number (6.022 x 1023) for each number of moles given below.,a) 1.06 moles,b) 0.98 moles,c) 8.96 moles

A student has a sample containing 1.94 x 1026 copper (1) iodide molecules. How many grams of copper (I) iodide does the student have

A student has a 3.64 g sample of CuCNS. How many molecules of CuCNS exist in this sample

a) A student has a 0.63 g sample of SbS3. How many molecules of SbS3 exist in this sample,b) In the same sample, how many Sb atoms are present

How many atoms are present in each of the following samples,a) 0.386 mol of HO,b) 5.48 g of SiO2,c) a mixture of 2.45 g of FeO3 and 1.81 g of NiO

If it takes 54.0 mL of 0.1 M NaOH to neutralize 125 mL of an HCI solution, what is the HCI

If it takes 25 mL of 0.05 M HCI to neutralize 345 mL of NaOH solution, what is the NaOH

If it takes 50 mL of 0.5 M KOH solution to completely neutralize 125 mL of HSO4 solution, what is the HSO4

In a titration with methyl orange as the indicator, 25.0 cm of sodium hydroxide solution required 27.85 cm of 0.0487 mol dm sulphuric acid to produce a colour change. Calculate the concentration of the sodium hydroxide solution.

25.0 cm of potassium dichromate(VI) solution were acidified and treated with excess KI (aq). The liberated iodine was titrated with 24.4 cm of 0.102 mol dm Na2S2O3(aq). Calculate the concentration of the KCrO7 (aq). CrO72 14H 61 2Cr 7HO 312 2S2032 12 S406 21

0.80 g of impure chalk was reacted with 100cm of 1 mol dm hydrochloric acid (an excess). The mixture was filtered into a volumetric flask and madeup to 250cm. A 25.0cm portion of the solution required 8.5cm of 1 mol dm sodium hydroxide solution for neutralisation. What is the percentage of calcium carbonate in the impure chalk

A 1.0000 g sample of KCO3 is dissolved in enough water to make 250.0 mL of solution. A 25.00 mL aliquot is taken and titrated with 0.1000 M HCl KCO3(aq) 2HCl(aq) 2KCl(aq) HO(1) CO2(g) How many mL of HCI are used

A 0.4108 g sample of CaCO3 is added to a flask along with 15.00 mL of 2.000 M HCI. CaCO3(aq) 2HCl(aq) CaCl2 (aq) HO(l) CO2(g) Enough water is then added to make 250.0 mL of solution A. A 20.00 mL aliquot of solution A is taken and titrated with 0.1160 M NaOH. How many mL of NaOH are used

Refer to the atomic masses in the periodic table inside the front cover of this textbook. State the mass of Avogadros number of atoms for each of the following elements (a) Copper sulfur (b) Mercury helium (c) (d)

Calculate the number of sodium atoms in 0.120 mol Na.

Calculate the number of moles of potassium in 1.25 x 10 atoms K.

Calculate the molar mass for each of the following substances (a) silver metal, Ag (b) ammonia gas, NH, (c) magnesium nitrate, Mg(NO3)2

How many O molecules are present in 0.470 g of oxygen gas

Calculate the density of ammonia gas, NH3, at STP. (MM 17.04 gmol)

A fire extinguisher releases 1.96 g of an unknown gas that occupies 1.00 L at STP. What is the molar mass (gmol) of the unknown gas
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What is the mass of 3.36 L of ozone gas, 03, at STP

How many molecules of hydrogen gas, H, occupy 0.500 L at STP

TNT (trinitrotoluene) is a white crystalline substance that explodes at 240 C. Calculate the percent composition of TNT, CH(NO)3

In a laboratory experiment, 0.500 g of scandium was heated and allowed to react with oxygen from the air. The resulting product oxide had a mass of 0.767 g. Now, lets find the empirical formula for scandium oxide, Sc.O..

Glycine is an amino acid found in protein. An analysis of glycine gave the following data 32.0 carbon, 6.7 hydrogen, 18.7 nitrogen, and 42.6 oxygen. Calculate the empirical formula of the amino acid.

The empirical formula for fructose, or fruit sugar, is CHO. If the molar mass of fructose is 180 gmol, find the actual molecular formula for the sugar.

50.00 mL of 0.0426 M HOCI (K 3.5 x 10) is titrated with 0.1028 M NaOH.,Calculate the pH at the equivalence point for each of the following titrations a. 0.104 g sodium acetate (K5.6 x 1010) is dissolved in 25.0 mL of water and titrated with 0.0996 M HCI.

A 25.0mL sample of 0.100 M lactic acid (HC,H,O3, pK, 3.86) is titrated with 0.100 M NaOH solution. Calculate the pH after the addition of a. 0.0 mL of the NaOH.,b. 4.0 mL of the NaOH.

If 40.0 ml of 0.100 M HPO4 are required to titrate 150. ml of NaOH to the equivalence point, what is the molarity of the NaOH

A sample of HSO, it is titrated with 0.75 M KUH. If 370.6 mL of KOH are required to neutralize a 30.00 mL sample of sulfuric acid, what is the concentration of the sulfuric acid.

1. The quantity of organically bound nitrogen (orgN) released by acid digestion is referred to as Kjeldahl nitrogen. One method used to determine the Kjeldahl nitrogen content involves a back titration and is outlined below. a) A 10.00 mL sample is diluted to 100 mL with distilled water. b) A 25.00 mL aliquot of this diluted sample is pipetted

25.0 cm of a solution of sodium hydroxide solution required 21.5 cm of 0.100 moldm sulfuric acid for neutralisation. HSO4 (aq) 2 NaOH(aq) NaSO4(aq) 2 HO(1) Find the concentration of the sodium hydroxide solution in moldm. Give your answer to 3 significant figures.,Find the concentration of the sodium hydroxide solution in gdm. Give your answer

Find the volume of 1.20 moldm hydrochloric acid that reacts with 25.0 cm of 1.50 moldm sodium hydroxide. Give your answer to 3 significant figures. HCl(aq) NaOH(aq) NaCl(aq) HO(l)

25.0 cm of arsenic acid, H3ASO4, required 37.5 cm of 0.100 moldm sodium hydroxide for neutralisation. 3 NaOH(aq) H3ASO4(aq) Na3AsO4(aq) 3 HO(l) Find the concentration of the arsenic acid in moldm. Give your answer to 3 significant figures.,Find the concentration of the arsenic acid in gdm. Give your answer to 3 significant figures.

What volume of 0.0400 moldm calcium hydroxide just neutralises 25.0 cm of 0.100 moldm nitric acid Give your answer to 3 significant figures Ca(OH)2(aq) 2 HNO3(aq) Ca(NO3)2(aq) 2 HO(1)

A series of titrations was carried out to find the concentration of the ethanoic acid in white vinegar. CH3COOH(aq) NaOH(aq) CH3COONa (aq) HO(l) In each titration, a student placed 25.0 cm samples of the vinegar in a conical flask. She then added a few drops of the indicator phenol red. She titrated the vinegar against a solution of sodium

A student prepares a combined standard solution by weighing out 252.6 mg of KNO3 and 148.5 mg of NaHPO43HO, dissolving in deionized water to a final mass of 102.234 g. After through mixing, 1.022 g of this solution were transferred to a clean dry container and diluted with deionized water to a final mass of 250.654 g. Calculate the final

The amount of iron in a meteorite was determined by redox titration using KMnO4 as the titrant. A 0.4185 g sample of the meteorite was dissolved in acid and the liberated Fe was quantitatively converted to Fe using a reducing column. Titrating this solution with 0.02500 M KMnO4 requires 41.27 mL to reach the endpoint. Determine the wt of FeO3 in

The Total Hardness of a water sample can be determined volumetrically using ethylenediamine tetraacetate (EDTA), which forms a 11 complex with Ca and other divalent metal cations. Calculate the Total Hardness and express as ppm CaCO3, if a 50.00 0.05 mL water sample required 3.22 0.03 mL of a (1.330 0.005) x 10 M EDTA titrant to reach a

A field portable volumetric analysis method for Total Alkalinity using a Hach Digital Titrator is based on the neutralization of bases in a water sample with the protons of a standardized sulfuric acid titrant (HSO4). The volume of titrant added is recorded with a digital counter which corresponds to the delivery of 1.25 L and can be converted to

The following method is reported in Standard Methods for the Examination of Water and Wastewater for the analysis of sodium hypochlorite (NaOCI) in bleach. . a 20.00 mL sample of bleach is diluted to 100.0 mL. a 25.00 mL aliquot of the diluted sample is then transferred into a flask and treated with an excess acidic iodide solution. the iodine

A 64.3 mg sample of a protein (MW 58,600) was treated with 2.00 mL of 0.0487 M sodium periodate (NaIO4) to selectively react with all of the serine and threonine residues. The resulting solution was then treated with excess iodide ion to convert the unreacted periodate into triiodide ion (13). 10 31 HO 103 13 OH A microtitration of the

2 Suppose a student a titration of an unknown Experiment conducted solution of the weak acid HNO2 with .0.265 M NaOH. First, the student diluted 15.0 mL1 of the HNO2 solution with 85.0 mL of water in an Erlenmeyer flask and added 2 drops of the indicator, phenolphthalein. Then, 0.265 M NaOH was titrated into the diluted HNO2 solution until the

Company A and Company B have the same total assets, Return on Assets (ROA), and profit margin. However, Company A has higher liabilitytoasset ratio and interest expense than Company B. Which of the following statements is most correct Select one a. Company A has a lower ROE than Company B. b. Company A has a lower operating income (EBIT) than

The following information is given Spot rate RMS Spot rate RM One month forward RMS 1090 One month forward RM 2085 RM2.45654633 RM5.03230400 Three months interest in Malaysia is 5.5, in Singapore is 4.0 and in Italy is 3.5. i) If you have RM570,250 today, determine how much S would you exchange with. (2 marks) ii) If you have 420,000 today,

A ray of light travelling in air falls obliquely on the surface of a calm pond. It will (a) go into the water without deviating from its path (b) deviate away from the normal (c) deviate towards the normal (d) turn back on its original path

The diameter of the reflecting surface of spherical mirror is called its (a) aperture (b) focal length (c) radius of curvature (d) none of these

Choose the incorrect statement. (a) The height of the object is taken to be positive as the object is usually placed above the principal axis. (b) The height of the image should be taken as positive for both virtual and real image. (c) A negative sign in the value of the magnification indicates that the image is real. (d) A positive sign in the

If the magnification of a lens has a positive value, the image is (a) real (c) inverted (b) virtual and erect (d) none of these

An object is placed at the centre of curvature of a concave mirror. The distance between the image and the pole is (a) equal to f (c) equal to 2f (b) greater than f but less than 2f (d) greater than 2f

If the magnification of a lens has a negative value, the image is (a) real and inverted (b) virtual (c) erect (d) none of these

R The focal length, f is valid (a) for convex mirror but not for concave mirror. (b) for concave mirror but not for convex mirror. (c) for both convex and concave mirrors. (d) neither for convex mirror nor for concave mirror.

The image of the distant object is obtained on a screen by using a concave mirror. The focal length of the mirror can be determined by measuring the distance between (a) the object and the mirror (b) the object and the screen (c) the mirror and the screen (d) the mirror and the screen as well as that between the object and the screen

Which of the following can make a parallel beam of light when light from a point source is incident on it (a) Concave mirror as well as convex lens (b) Convex mirror as well as concave lens (c) Two plane mirrors placed at 90 to each other (d) Concave mirror as well as concave lens

Under which of the following conditions a concave mirror can form a real image larger than the actual object (a) When the object is kept at a distance equal to its radius of curvature (b) When object is kept at a distance less than its focal length (c) When object is placed between the focus and centre of curvature (d) When object is kept at a

Rays from Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that size of its image is equal to the size of the object (a) 15 cm in front of the mirror (b) 30 cm in front of the mirror (c) between 15 cm and 30 cm in front of the mirror (d) more than 30 cm in front of the mirror

TMI,Which one of the following ray diagrams is correct for the ray of light incident on a lens as shown in figure NCERT Exemplar 3 NTI Nall

Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in Figure NCERT Exemplar (a) u F 2F,(c) O F

You are given water, mustard oil, glycerine and kerosene. In which of these media a ray of light incident obliquely at same angle would bend the most (a) Kerosene (c) Mustard oil (b) Water (d) Glycerine

A child is standing in front of a magic mirror. He finds the image of his head bigger, the middle portion of his body to be of same size and that of the legs smaller. Which of the following is the order of combinations for the magic mirror from the top (a) Plane, convex and concave (b) Convex, concave and plane (c) Concave, plane and convex (d)

Two lenses of power 2.50 D and 3.75 D are combined to form a compound lens. Its focal length in cm will be (a) 40 (b)40 (c) 80 (d)80

A man runs towards the plane mirror at 2 ms. The relative speed of his image with respect to him will be (a) 2 ms (b) 4 ms (c) 8 ms (d) 10 ms

An object is placed 20 cm in front of a plane mirror. The mirror is moved 2 cm towards the object. The distance between the positions of the original and final images seen in the mirror is (a) 2 cm (b) 4 cm (c) 10 cm (d) 22 cm

Which position of the object will produce a magnified virtual image, if a concave mirror of focal length 15 cm is being used (a) 10 cm (b) 20 cm (c) 30 cm (d) 35 cm

A concave mirror produces a magnification of 4. The object is placed (a) At the focus (b) Between focus and centre of curvature (c) Between focus and pole (d) Beyond the centre of curvature

Two big mirrors A and B are fitted side by side on a wall. A man is standing at such a distance from the wall that he can see the erect image of his face in both the mirrors. When the man starts walking towards the mirrors, he finds that the size of his face in mirror A goes on increasing but that in mirror B remains the same (a) Mirror A is

A ray of light is travelling in a direction perpendicular to the boundary of a parallel glass slab. The ray of light (a) Is refracted towards the normal (c) Is reflected along the same path (b) Is refracted away from the normal (d) Does not get refracted

A ray of light passes from a medium X to another medium Y. No refraction of light occurs if the ray of light hits the boundary of medium Y at an angle of (a) 120 (b) 90 (c) 45 (d) 0

A lens of focal length 12 cm forms an erect image, three times the size of the object. The distance between the object and image is (a) 8 cm (b) 16 cm (c) 24 cm (d) 36 cm

A student does the experiment on tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence. He can get a correct measure of the angle of incidence and the angle of emergence by following the labelling indicated in figure (a) A (A) (b) B (B) (c) C (C) (d) D (D)

A student traces the path of a ray of light passing through a rectangular slab. qaza C A B For measuring the angle of incidence, he must position the protractor in the manner shown in the figure (a) A (b) B (c) C (d) D

A student traces the path of a ray of light passing through a rectangular slab for three different values of angle of incidence (Zi) namely 30, 45 and 60. He extends the direction of incident ray by a dotted line and measures the perpendicular distance l between the extended incident ray and the emergent ray. He will observe that (a) I keeps on

Focal length of plane mirror is (a) At infinity (c) Negative (b) Zero (d) None of these

Image formed by plane mirror is (a) Real and erect (c) Virtual and erect (b) Real and inverted (d) Virtual and inverted

A concave mirror gives real, inverted and same size image if the object is placed (a) At F (d) Beyond C (b) At infinity (c) At C

In optics, an object which has higher refractive index is called (a) Optically rarer (b) Optically denser (c) Optical density (d) Refractive index

The unit of power of lens is (a) Metre (b) Centimetre (c) Dioptre (d) M

The radius of curvature of a mirror is 20cm the focal length is (a) 20 cm (b) 10 cm (c) 40 cm (d) 5 cm

An object is placed at a distance of 0.25 m in front of a plane mirror. The distance between the object and image will be (a) 0.25 m (b) 1.0 m (c) 0.5 m (d) 0.125 m

The angle of incidence for a ray of light having zero reflection angle is (a) 0 (b) 30 (c) 45 (d) 90
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For a real object, which of the following can produce a real image (a) Plane mirror (b) Concave mirror (c) Concave lens (d) Convex mirror

Which of the following mirror is used by a dentist to examine a small cavity (a) Convex mirror (b) Plane mirror (c) Concave mirror (d) Combination of convex and concave mirror

A concave mirror of radius 30 cm is placed in water. Its focal length in air and water differ by (a) 15 (b) 20 (c) 30 (d) 0

An object at a distance of 15 cm is slowly moved towards the pole of a convex mirror. The image will get (a) shortened and real (c) enlarged and virtual (b) enlarged and real (d) diminished and virtual

The image formed by concave mirror is real, inverted and of the same size as that of the object. The position of object should be (a) at the focus (c) between focus and centre of curvature (b) at the centre of curvature (d) beyond centre of curvature

The nature of the image formed by concave mirror when the object is placed between the focus (F) and centre of curvature (C) of the mirror observed by us is (a) real, inverted and diminished (c) real, inverted and enlarged (b) virtual, erect and smaller in size (d) virtual, upright and enlarged

The angle of incidence i and angle of refraction r are equal in a transparent slab when the value of i is (a) 0 (c) 90 (b) 45 (d) depend on the material of the slab

The refractive index of transparent medium is greater than one because (a) Speed of light in vacuum speed of light in transparent medium (b) Speed of light in vacuum speed of light in transparent medium (c) Speed flight in vacuum speed of light in transparent medium (d) Frequency of light wave changes when it moves from rarer to denser medium

You are given three media A, B and C of refractive index 1.33, 1.65 and 1.46. The medium in which the light will travel fastest is (a) A (b) B (c) C (d) equal in all three media

Light from the Sun falling on a convex lens will converge at a point called (a) centre of curvature (b) focus (c) radius of curvature (d) optical centre