Electopositivity is the measure of the ability of elements to donate electrons to form positive ions. Whereas the Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Group 1 is more electropositive than group 17 and group 17 is more electronegative than group 1.
76 What number of significant figures is used to express the concentration of the KOH (aq)?
77 Complete the equation in your answer booklet for the neutralization reaction that occurs during the titration.
HCl + KOH--> ________________
78 Determine the concentration of the HCl(aq) solution, using the titration data.
79 Describe one laboratory safety procedure that should be used if a drop of the KOH(aq) is spilled on the arm of the student.
The precaution taken when KOH is dropped on the arm of a student is to apply plenty water over the affected area.
The term titration has to do with a reaction between an acid and a base to form salt and water only.
In this reaction, we have; KOH + HCl -----> KCl + H2O. The concentration of KOH was expressed to two significant figures.
The concentration of HCl is obtained from;
0.150 M * 18.5 mL * 1/25.0 mL * 1 = 0.11 M
The precaution taken when KOH is dropped on the arm of a student is to apply plenty water over the affected area.
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Answer is: A. test and determine the pH values of unknown solutions.
Acid-base indicators are usually weak acids or bases and they are chemical detectors for hydrogen or hydronium cations (pH or pOH values).
Example for acid-base indicator is phenolphthalein (molecular formula C₂₀H₁₄O₄). Phenolphthalein is colorless in acidic solutions and pink in basic solutions.
Another example is methyl orange. It is red colour in acidic solutions and yellow colour in basic solutions.
Answer: The correct answer is option A.
Explanation:
An indicator is a substance which changes color to show any chemical change happening in the reaction. It gives the visible sign of any change.
Hence, main role of indicators from the given options is to determine the pH values of unknown solutions.
pH is the scale which shows the acidity and basicity of the solutions. It is the negative logarithmic value of hydrogen ion concentration of the solution. More the hydrogen ion concentration, less will be the pH and more acidic will be the solution.
The scale ranges from 0 to 14.
The value ranging from 0 to 6.9 are acidic solutions.
The value ranging from 7.1 to 14 are basic solutions.
The value having pH = 7 is neutral solution.
Indicator used to determine the pH of the solution is pH-paper which is shown in the image.
What conditions must be specified when expressing the solubility of a substance
Solubility means the ability of a solute to dissolve in solvent to form a solution.
The temperature and pressure must be specified when expressing the solubility of a substance.
Solubility is defined as the maximum amount of a substance that will dissolve in a given amount of solvent at a particular temperature.
The solute can be a solid, liquid or a gas.
The solubility of a solid or a liquid solute in a solvent is affected by the temperature, while the solubility of a gaseous solute is affected by both the temperature and the pressure of the gas.
Temperature must be specified because solubility varies with temperature. For gases, the pressure must also be specified. Solubility is specific for a particular solvent.
Therefore, Solubility means the ability of a solute to dissolve in solvent to form a solution.
The temperature and pressure must be specified when expressing the solubility of a substance.
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B. 6
C. 2
D. 10
Answer : The correct option is, (A) 8
Explanation :
Octet rule : It is the tendency of atoms to have eight electrons in the valence shell. When the atoms have fewer than eight electrons then they tend to react and form the more stable compounds.
Or we can say that the atoms attempt to get a noble gas electron configuration, which is eight valence electrons.
For example : As we know that the sodium has one valence electron, so if giving it up then the result in the same electron configuration as the neon and chlorine has seven valence electrons, so if it takes one it will have eight and the result in the same electronic configuration as the argon.
Hence, the correct option is, (A) 8