24. A reaction that place between dissolved barium nitrate and dissolved sodium

Question

24. A reaction that place between dissolved barium nitrate and dissolved sodium sulfate results in formation of solid takes sulfate. Which equation describes this reaction? b. BaNOs(aa) Naso(aq) Basou NaNOs(aq) c. Ba(Noson(ag) Na2so4(aq) Baso4(s)+2NaNO,(aq) 25. An irregularly shaped metal object with a mass of 25.43 g was placed in a graduated cylinder with water. The before and after volumes are shown below. What is the density of the metal? 40 mL. 40 mL. 35 mL 35 mL, 30 mL. 30 mL 25 mL. 25 mL. -20 mL 20 ml. 15 mL 15 mL 10 mL. 10 mL alter before d. 0.344 glcm3 a. 2.906 g/cm' e. 2.734 b. 0.782 g/cm' c, 2.8 g/cm

Explanation / Answer

Solution:- (24) Barium is second group metal with +2 charge and nitrate ion is NO3 with -1 charge, So, the formula of Barium nitrate is Ba(NO3)2 . Sodium is first group metal with +1 charge and sulfate ion is SO4 with -2 charge so the formula of sodium sulfate is Na2SO4. Both of these are water soluble so we will write (aq) for them. When they are mixed a precipitation reaction takes place and we get a precipitate of Barium sulfate, BaSO4 and we write (s) for the insoluble ones that is for precipitates. So, the reaction will be..

Ba(NO3)2(aq) + Na2SO4(aq) ------------> BaSO4(s) + 2NaNO3(aq)

so, choice (c) is correct.

(25) mass of metal is given = 25.43 g

density = mass/volume

when metal is placed in graduated cylinder filled with water then level of water rises in the cylinder and volume increases. The difference of these two volumes (final - initial) is the volume of metal.

To read the volume in graduated cylinder we look at the bottom line of the meniscus. in the first cylinder before the metal added, the meniscus is between 23 and 24 so the volume is 23.5 ml. In second cylinder the meniscus is between 32 and 33 so the volume is 32.5 ml. So, the volume of the metal is = 32.5 ml - 23.5 ml = 9.0 ml

density of metal = 25.43g/9.0ml = 2.8 g/ml or 2.8 g/cm3 (since 1 ml = 1 cm3)

Answer is with two sig figs since volume is 9.0 ml and it has only two sig figs.

so, correct choice is (c) 2.8 g/cm3.

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