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Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

What do you understand by the statement "the solubility of copper sulphate in water at $20^{\circ}C$ is 20.7 g" ?

  1. A maximum of 20.7 grams of copper sulphate can be dissolved in 100 ml water at a temperature $20^{\circ}$C.
  2. A maximum of 20.7 grams of copper sulphate can be dissolved in 100 g of water at $20^{\circ}$C.
  3. A maximum of 20.7 grams of copper sulphate can be dissolved in 79.3 g of water at $20^{\circ}$C.
  4. A maximum of 20.7 grams of copper sulphate can be dissolved in 79.3 ml of water at $20^{\circ}$C.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solubility is given in grams per 100 gm of water with temperature and 1 atmospheric pressure.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

In the solvation of $NaCl$ in water, which of the following occur ?

  1. Hydrogen atom interacts with $Cl^-$ atom
  2. Oxygen atom interacts with $Na^+$ atom
  3. Both $A$ and $B$

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the water molecule oxygen has higher electronegativity than hydrogen thus has a partial negative charge and hydrogen has a partial positive charge. So during the solvation of NaCl in water, hydrogen atoms interact with chlorine anion and oxygen interact with sodium cation.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

______ is the chief component of natural gas.

  1. Ethane

  2. Methane

  3. Propane

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

Natural gas is a fossil fuel. It is used for cooking, heating and electricity generation. It is found deep underground rock formation. It is a naturally occurring hydrocarbon gas mixture consisting primarily of methane. It is also used as fuel for vehicles.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

At ${25}^{o}C$ the solubility of ${Ag} _{2}{CO} _{3}$ (${K} _{sp}=4.3\times {10}^{-13}$) would be in what order in the following solutions?

  1. $0.01M$ $Ag{NO} _{3}$
  2. $0.04M$ ${K} _{2}{CO} _{3}$

  3. pure water
  4. in a buffer ($pH=4$)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The solubility of Ag2CO3 is suppressed by the common ion effect. Ag+ from AgNO3 will significantly decrease the solubility of Ag2CO3 more than the other options provided.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

$Ca _3(PO _4) _2$ is insoluble in water. On adding a few drops of HCl to solid $Ca _3(PO _4) _2$ in contact with water, the solid dissolves. The reason is?

  1. The solvent becomes more polar on adding HCl
  2. $Ca _3(PO _4) _2$ combines with HCl to form soluble $CaCl _2$
  3. $Ca(H _2PO _4) _2$ is formed, which dissolves
  4. $H _3PO _4$, a weak acid is formed and the solubility product of $Ca _3(PO _4) _2$ decrease
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Calcium phosphate is a salt of a weak acid (phosphoric acid). Adding hydrochloric acid introduces strong H+ ions that combine with phosphate ions to form soluble calcium dihydrogen phosphate or phosphoric acid, causing the solid to dissolve.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

The solubility of $A {2}X _{3}$ is $y$ $mol$ $dm^ {-3}$. Its solubility product is ____________.

  1. $6y^ {4}$
  2. $64y^ {4}$
  3. $36y^ {5}$
  4. $108y^ {5}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For a salt A2X3 dissociating into 2A(3+) and 3X(2-), if solubility is y, [A(3+)] = 2y and [X(2-)] = 3y. The solubility product Ksp = (2y)^2 * (3y)^3 = 4y^2 * 27y^3 = 108y^5.

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

What is the solubility of $Al(OH _{3}), K _{sp} = 1 \times 10^{-33}$, in a solution having $pH = 4$?

  1. $6 \times 10^{-3}$M
  2. $10^{-6}$M
  3. $1.5 \times 10^{-4}$M
  4. $2.47 \times 10^{-9}$M
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The solubility equilibrium of $Al(OH) _3$ is

$Al(OH) _3$ ${\rightarrow} _{\leftarrow}$ $Al^{+3}$  + $3OH^-$
Therefore $x=1,\ y=2$ and $K _{sp}$=$[Al^{+3}]\times [OH^-]$ = $27S^4$
$S$ = $(\dfrac{10^{-33}}{27})^{1/4}$
Therefore $S$= $2.47\times 10^{-9}M$ in $ mol\ dm^{-3}$

Multiple choice chemistry nature of things objects that float or sink substances that sink or float soluble and insoluble substances

Which of the following is most soluble?

  1. ${Bi} _{2}{S} _{3} \left({K} _{sp} = 1\times {10}^{-17}\right)$
  2. $MnS\left({K} _{sp} = 7\times {10}^{-16}\right)$
  3. $CuS\left({K} _{sp} = 8\times {10}^{-37}\right)$
  4. ${Ag} _{2}S\left({K} _{sp} = 6\times {10}^{-51}\right)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ksp (Solubility product constant) is the equilibrium between a solid and its respective ions in a solution. The value of the constant identifies the degree to which the compound can dissociate in water. The higher the Ksp the more soluble the compound is.
Bismuth is a large ion and sulphur is a small ion, the attractive forces between them are high thus the solubility is high. The solubility product can be calculated as :
$Bi _2S _3$
$K _sp = 1 \times 10^{-17}$
$K _sp = [Bi]^2 [S]^3$
$1 \times 10^{-17} = (2x)^2 (3x)^3 = 108x^5$
$x^5 = \dfrac{1 \times 10^{17}}{108} = 0.000156M $