Question

1. A substance is orange in methyl orange, purple in crystal violet, yellow in bromthymol blue, colorless in phenolphthalein, green in bromcresol green, and yellow in allizarin yellow-R. What is the narrowest pH range it can have? Explain: 2. Write the balanced equation for the reaction of NaOH with H2S04: 3. (a) Why do we run the titrant from the burette into a waste beaker before beginning the titration? (b) How much HCl do we initially add to our erlenmeyer flask in Part 2?

Answer 1

Transition pH Lange high Indicator Low pH color I. Methyl Orange Red 3. All zarine Yellowr yellow 3. Bromos resol yellow pH color 3.1 – 4.4. 10.2-1210 R Orange a red Blue 4.0-5.6 Blue . . green 4. Bromothymol S blue S. phenolphthalein 6. Cresol Red : yellow 'colourless : Yellow 60-706 8.3-1010 7.2-8.8 Dark pink Redolish-purple Ti
. A list of some common pH indicator solutions.
Bromothymol Blue 4 5 6.5 4 7.0 7.5 useful range
. We used Bromothymol Blue in the acid rain demonstration.These indicators are normally used over a fairly short range of pH values (indicated in the table above). As a pH indicator, bromothymol blue, for example, would be useful between from about pH 6.0 to pH 7.6. Other indicators work in different pH ranges. Using bromothymol blue you wouldn't be able to distinquish between an acid with pH 4 from an acid with pH 5. They would both appear yellow. Similarly solutions with pH 9 and pH 10 would both appear blue (vivid blue). With bromothymol blue you could hope to identify solutions with pH 6.5 (yellowish green), pH 7 (green) and, and pH 7.5 (bluish green).

^{2.answer:- Balanced equation 2NaOH+ H2SO4 ------> Na2SO4 + 2H2O}

^{3.(a)answer:-} If the buret is used without removing the water first, the results will likely be inaccurate as water may affect the concentration of the solution inside. We must rinse it first with NaOH as it lessens the amount of water in the system and increases the amount of NaOH inside.

3(b).answer:- use a volumetric pipet to transfer exactly 10 mL of stock HCl into a 125 mL Erlenmeyer flask.

4. Using equation N₁V_{1 =} N₂V₂

Given:- N₁= 0.175N, V₁= 26.3ml, V₂= 35ml , N₂=?

N₂= (0.175 × 26.3)/(35)= 0.1315N

Answer- 0.1315N of Ca(OH)₂

5.answer:- complete balanced equation:-

H₂CO₃ + 2NaOH -------> Na₂SO₄ + 2H₂O

HNO₃ + RbOH --------> RbNO₃ + H₂O

6. Produced product following neutralization reaction.

2HCl + Ca(OH)₂ --------> CaCl₂ + 2H₂O

3NaOH + H₃PO₄ ------> Na₃PO₄ + 3H₂O

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