Chemistry

Solutions and pH Chemistry

451 Questions

Solutions and pH chemistry focus on the acidity or alkalinity of various substances, from human urine to acidic soils. Questions involve titration calculations, molarity determination, and understanding mole fractions. This topic is a staple in the chemistry sections of state and national level competitive exams.

Calculating solution molarityMole fraction calculationpH value interpretationAcidic soils and pHTitration and neutralization

Solutions and pH Chemistry Questions

Multiple choice chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

Find the $pH$ of the resulting solution and then mark the option in which $pH$ exists between color transition range of an indicator.

50 ml of 0.2M HA solution $(K _a=10^{-5})$ + 50ml of 0.1M HCl solution + 100 ml of 0.13 M NaOH solution.

  1. Phenol red (6.8 to 8.4)

  2. Propyl red (4.6 to 6.4)

  3. Phenolphthalein (8.3 to 10.1)

  4. Malachite green (11.4 to 13)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Milimoles of HCl = Volume (ml) $\times$ Molarity = $50\times 0.1=5$ milimoles.
Milimoles of NaOH $=100 \times 0.13=13$ milimoles.

Some of the NaOH will be neutralized by HCl.
Milimoles of NaOH remaining unreacted $13-5=8$ milimoles.

Milimoles of HA$=50 \times 0.2 =10$ milimoles.
Out of this 8 milimoles will be neutralized to form a salt.

Thus the solution now contains 2 milimoles of weak acid HA and 8 milimoles of its salt with strong base.

It is an acidic buffer solution.
The expression for the pH of the acidic buffer solution is as given below.

$pH=pK _a+log \frac {[salt]} {[acid]}$

$pK _a=-log10^{-5}=5$

$pH=5+log \frac {8} {2}=5.6$.

Thus the suitable indicator is propyl red with pH range 4.6 to 6.4.

Multiple choice maths fraction one fraction, many forms use of decimals in measure of length decimal fractions in the units of currency, length, weight, capacity

How much pure alcohol should be added to $400 ml$ of strength $15\%$ to make its strength $32\%$?

  1. $50 ml$
  2. $75 ml$
  3. $100 ml$
  4. $150 ml$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The amount of alcohol in $400ml$ solution of $15\%$ strength

$=400\times \cfrac { 15 }{ 100 } ml=60ml$

Let the required amount of alcohol to be added $=x$ ml.
It will increase the amount of the solution by $x$ ml.

$\therefore $ The amount of alcohol now $=(60+x)ml$
and the amount of the solution$=(400+x)ml$.
Then, the strength $=32\%=\cfrac { 60+x }{ 400+x } =\cfrac { 32 }{ 100 }$

$\Rightarrow 25x+1500=3200+8x\ \Rightarrow 17x=1700\ \Rightarrow x=100$.
So, the required amount of pure alcohol to be added $=100 ml$.

Multiple choice botany cell cycle difference between meiosis and mitosis division for growth and reproduction meiosis

........... is used for preparing standard solutions in which it is always desired to maintain a constant pH.

  1. Buffer

  2. Plasma

  3. Serum

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A buffer is a solution that resists a change in pH upon the addition of acidic or basic components. To effectively maintain a pH range, a buffer consists of a weak conjugate acid-base pair. It is either a weak acid and its conjugate base, or a weak base and its conjugate acid. Thus the correct answer is option A.

Multiple choice botany cell cycle difference between meiosis and mitosis division for growth and reproduction meiosis

If the activity of an enzyme is constant over a broad range of pH values,it is likely that

  1. only ionizing groups on the enzyme participate in the reaction

  2. only ionizing groups on the substrate participate in the reaction

  3. ionizing groups on the enzyme and substrate participate in the reaction

  4. the temperature should be changed in order to observe a pH effect
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Changes in pH may influence the state of a catalyst as well as change the shape or charge properties of the substrate so that either the substrate can not tie to the dynamic site or it can't experience catalysis. In general, protein has a pH ideal. Anyway, the ideal isn't the equivalent for every chemical. 
So, the correct option is 'only ionizing groups on the enzyme participate in the reaction'
Multiple choice bio-chemistry digestive system of human digestive system- glands mouth and buccal cavity digestive glands

What is optimum pH for the action of salivary anylase?

  1. $1.8$
  2. $6.8$
  3. $7.4$
  4. $8$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The optimum pH for the enzymatic activity of salivary amylase ranges from 6 to 7. Above and below this range, the reaction rate reduces as enzymes get denaturated. The enzyme salivary amylase is most active at pH 6.8. 

So, the correct option is '6.8'.

Multiple choice evs water in our life where do we get water from? why conserve water uses of water

Which pH range is most conducive for fresh water plants and animals?

  1. 2.0 -3.5

  2. 3.5 -5.0

  3. 6.5 -7.5

  4. 8-9
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Most fresh water organisms thrive in a near-neutral pH range, typically between 6.5 and 7.5. Values significantly lower (acidic) or higher (alkaline) can be harmful to aquatic life.

Multiple choice chemistry electrolysis electrolytes and non-electrolytes introduction to electrolysis chemical reactions

The equivalent conductance at infinite dilution of an acid like HF

  1. Can be determined by extrapolation of measurements of dilute solutions of HCI, HBr and HI

  2. Can be determined by measurement of very dilute HF solution

  3. Can best be determined from measurements of concentrated solutions of NaF, NaCI and HCI

  4. Can best be determined from measurements of dilute solutions of NaF, NaCI and HCI.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The equivalent conductance at infinite dilution of an acid like $HF$ can best be determined from measurement of dilute solution of $NaF,NaCl,HCl$ because these have ionic character.

Multiple choice salts salts and their classification acids, bases and salts chemistry

${ H } _{ 3 }{ PO } _{ 4 }$ is a tribasic acid and one of its salt is $Na{ H } _{ 2 }{ PO } _{ 4 }$. What volume of 1M NaOH solution should be added to 12g $Na{ H } _{ 2 }{ PO } _{ 4 }$ to convert it into $Na _{ 3 }{ PO } _{ 4 }$? (at.wt of P=31)

  1. 100 mL

  2. 200 mL

  3. 80 mL

  4. 300 mL
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$NaH _2PO _4$ + $ 2 NaOH $ $ \rightarrow Na _3PO _4 + H _2O $

From the above reaction we can say that,
1 mol of $NaH _2PO _4$ reacts with 2 mol of NaOH.
Molar mass of $NaH _2PO _4$  = 120 g / mol
12g of $NaH _2PO _4$ contains = 0.1 mol
So the number of moles of NaOH required = 0.2 mol
Molarity of NaOH = 1M
1 mol = 1000 ml
0.2 mol = ?
So, the volume of 1M NaOH solution = 200 ml

Multiple choice salts salts and their classification acids, bases and salts chemistry

Equal volumes of $1\ M$ $HCl$ and $1\ M$ $H _2SO _4$ are neutralized by dilute NaOH solution liberating $x$ kcal and $y$ kcal heat. Which of the following is correct?

  1. $x=y$
  2. $x=0.5y$
  3. $x=0.4y$

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Reaction involved are:
$HCl+NaOH \rightarrow NaCl+H _2O, \Delta H _1=xkcal$
$H _2SO _4+2NaOH \rightarrow Na _2SO _4+2H _2O, \Delta H _1=ykcal$
(i) acid-base neutralization reaction for HCl is represented as:
$H^++OH^- \rightarrow H _2O, \Delta H _1=xkcal$
(ii) acid-base neutralization reaction for $H _2SO _4$ is represented as:
$2H^++2OH^- \rightarrow 2H _2O, \Delta H _1=ykcal$
since reaction (ii) is twice of reaction (i), so is the enthalpies
thus $2x=y$
or $x=0.5y$