dispensed into the of NaOH had been in 3omL of water When the pink color persist

Question

dispensed into the of NaOH had been in 3omL of water When the pink color persisted, 51nm beaker. What is the molarity of NaOH? 13) In the reaction of HCO,NaOHHO NaCHO. a 3g sample a) 29M b).06M c)36M d) 4.0M e) 1.7M e) Volumetric point a) Equivalence point b) Indicator point c) Standard poin 15) What is the confirmatory test that lead chioride exists in an unknown solution? 14) The point in a titration at which the indicator changes is called the a) black solid o) white solid c) orange solid d) clear solution with bubbles 16) Centrifuging the solution means a) packing the precipitates to the bottom of test tube b) pouring the solution without disturbing the precipitate c) pouring both the precipitate and solution to a new test tube d) adding acid to the solution to adjust pH ?At 741 mmHg and 44 ?, 7.10g of a gas occupy a volume of 5.40L. What is the molar mass of the c) 35.0 g/mo gas (R= 0821?atmmol.K,760mmHg·1 atrm)? d) 1.48 g/mol e) 62.4 g/mol a) 153. 7 gmol b) 11077 g/mol 18) Dumas method is useful only for gaseous samples because a) All the liquids have very high boiling points that cannot be achieved in a standard laborato b) Ideal gas law PV nRT can be applied only to gaseous samples c) Only gaseous samples can escape through a pinhole on the capillary stopper d) Handling gaseous samples is easier than liquid or solids samples e) Pressure of liquids is hard to measure 19) Choose the correct statement a)Acid-base neutralization is endothermic b)Enthalpy change for neutralization of any weak acid- weak base is the same c)Theoretically, strong acid- strong base neutralization should have bigger enthalpy chang than that of weak acid- weak base neutralization d)SH is a pathfunction, and therefore the value of ?? is independent of the path )Enthalpy values are always positive

Explanation / Answer

14. Answer is option A= 0.29 M .Molarity of NaOH can be calculated by formula,

M=g of HC8H4O4 X1000 / mlof NaOH X mol.wt.of HC8H4O4 (204M)

M=3gm X1000 / 204X 51=0.29M.

15. The point in a titration at which the indicator changes is called Equivalence point. The equivalent point at which the equivalent amount of acid and base are mixed. The end point that means in titration when indicator added the colour of the solution get changed that point is called Equivalence point.

16. Centrifuging the solution means packing the precipitate to the bottom of the test tube. e Centrifugation technique involves spinning of the solution by applying centrifugal force. This process completly seperate the precipitate from the solution and the precipitate get packed at the bottom of the centrifugal tube and upper layer of the tube contain solution.

17. Answer is option C 35.0g/mol. Molar mass is calculated by equation PV=nRT

Here P= 741mmHg. Convert it into atm.= 0.975 atm (given 760mmHg=1atm so 741mmHg=0.975atm)

V=5.40L, n=we have to calculate, R= 0.0821L atm/mol, T=44°C. convert it into kelvin, 317.15 K.

now, n=PV/RT

n= 0.975 X 5.40 / 0.0821 X 317.15

n= 0.2022 mol.

now divide g by moles to get molar mass,

we have 7.10g of gas

therfore, molar mass = 7.10 / 0.2022 = 35.0 g/mol.

18. Dumas method useful for gaseous samples because all liquids have high boling point that can not be achieved. Most of the liquids have high boiling point which can cause error while determination of density by dumas method.

19. Correct statement is Strong acid stron base neutralisation should have bigger enthalpy change than the weak acid and weak base neutralisation. Strong acid strong base gives similar enthalpy values. In neutralisation of strong acid and strong base the reaction takes place by hydrogen ions and hydroxide ions. The other ions does not take part in reaction. therefore enthalpy is same. While in weak acid and weak base the acid ions are actually not ionised therfore enthalpy terms includes ionising acids as well as hydrogen and hydroxide ions. therefore change in enthalpy occurs.

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