Tag: chemical formula and mole concept

Quizzes (3) Questions (24)

Questions Related to chemical formula and mole concept

Multiple choice introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

A definite mass of $ H _{2}O _{2} $ is oxidized by excess of acidified $ KMnO _{4} $ and acidified $ K _{2}Cr _{2}O _{7} $, in separate experiments. Which of the following is/are correct statements? 
(K = 39, Cr = 52, Mn = 55 )

  1. Mass of $ K _{2}Cr _{2}O _{7} $ used up will be greater than that of $ KMnO _{4} $
  2. Moles of $ KMnO _{4} $ used up will be greater than that of $ K _{2}Cr _{2}O _{7} $

  3. Equal mass of oxygen gas is evolved in both the experiments.
  4. If equal volumes of both the solutions are used for complete reaction, then the molarities of $ KMnO _{4} $ and $ K _{2}Cr _{2}O _{7} $ solutions are in $6:5$ ratio.
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation

According to question, reaction of experiment (1) and (2)
(1)$ 5H _{2}O _2+2KMnO _{4}+3H _{2}SO _{4}\rightarrow 5O _{2}+2MnSO _{4}+K _{2}SO _{4}+8H _{2}O $


(2)$ 3H _{2}O _{2}+K _{2}Cr _{2}O _{7}+4H _2SO _{4}\rightarrow Cr _{2}(SO _{4}) _{3}+3O _{2}+K _{2}SO _{4}+7H _{2}O $

(a) According to reaction (1)
5 mole $ H _{2}O _{2} = 2\,mole KMnO _{4} $

1 mole $ H _{2}O _{2} = \dfrac{2}{5} = 0.4\,mole\,KMnO _{4} = 63.2\,g\,KMnO _{4} $

According to reaction (2)
3 mole $ H _{2}O _{2} = 1\,mole\,K _{2}Cr _{2}O _{7} $

1 mole $ H _{2}O _{2} = \dfrac{1}{3} mole\,K _{2}Cr _{2}O _{7} = 98.1 g \, K _{2}Cr _{2}O _{7} $

Mass of $ K _{2}Cr _{2}O _{7}> KMnO _{4} $

(b) Moles of $ KMnO _{4}> $ moles of $ K _{2}Cr _{2}O _{7} (0.333) $

(c)In reaction 1, 5 Mole $ H _{2}O _{2} $ released = 5 mole $ O _{2}\Rightarrow 32\times 5=160g $
In reaction 2, 3 mole $ H _{2}O _{2} $ released = 3 mole $ O _{2}=3\times 32= 96 g$ 

(d) 1 mole of $ H _{2}O _{2} = \dfrac{2}{5} $ moles $ KMnO _{4} $ exp...(1)
1 mole of $ H _{2}O _{2} = \dfrac{1}{3}$ mole $ K _{2}Cr _{2}O _{7} $ exp...(2)
$ \dfrac{KMnO _{4}}{K _{2}Cr _{2}O _{7}} = \dfrac{\dfrac{2}{5}}{\dfrac{1}{3}} = \dfrac{2}{5}\times \dfrac{3}{1} = \dfrac{6}{5}\Rightarrow 6:5 $

Options A, B and D are correct.

Multiple choice introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

Two acids $ H _{2}SO _{4} $ and $ H _{3}PO _{4} $ are neutralized separately by the same amount of an alkali when sulphate and dihydrogen orthophosphate are formed, respectively. Find the ratio of the masses of $ H _{2}SO _{4} $ and $ H _{3}PO _{4} $ 

  1. $ 1:1 $
  2. $ 1:2 $
  3. $ 2:1 $
  4. $ 2:3 $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$H _{2}SO _{4}+2NaOH\rightarrow Na _{2}SO _{4}+2H _{2}O$

$H _{3}PO _{4}+NaOH\rightarrow NaH _{2}PO _{4}+H _{2}O$

Equivalent of alkali $= 19$ eq of $H _{2}SO _{4}= 1g$ eq of $H _{3}PO _{4}$

Two acids must be reacting in the ratio of their equivalent masses

Eq. wt. of $H _{2}SO _{4}=\dfrac{98}{2}=49$

Eq. wt. of $H _{3}PO _{4}= \dfrac{98}{1}=98$

$\therefore $ ratio of masses of $H _{2}SO _{4}$ & $H _{3}PO _{4}$
$49:98=1:2$

$\Rightarrow 1:2$

Multiple choice introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

A gaseous alkane is exploded with oxygen. The volume of ${O} _{2}$ for complete combustion of alkane to $C{O} _{2}$ formed is in the ratio $7:4$. The molecular formula of alkane is:

  1. ${C} _{2}{H} _{6}$
  2. ${C} _{3}{H} _{8}$
  3. ${C} _{4}{H} _{10}$
  4. $C{H} _{4}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The balanced reaction is given below:


${C} _{n}{H} _{2n+2} +[n+\displaystyle\frac{n+1}{2}]{O} _{2}\rightarrow nC{O} _{2} +(n+1){H} _{2}O$

Given, 

$\displaystyle\dfrac{n+\dfrac{n+1}{2}}{n}=\dfrac{7}{4}\implies n=2$

Hence, the alkane is ${C} _{2}{H} _{6}$.

Hence, the correct option is $A$

Multiple choice chemistry chemical formula and mole concept introduction to mole gas laws and mole concept mole concept

A gaseous oxide contains 30.4% of nitrogen, one molecule of which contains one nitrogen atom. The density of the oxide relative to oxygen is:

  1. 0.94

  2. 1.44

  3. 1.50

  4. 3.0
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

100g of oxide contain 30.4 g of Nitrogen. 


Since 1 molecule contain one nitrogen atom

14 g Nitrogen is contained by Mol. wt of oxide.

30.4 g of nitrogen present in 100 g of oxide 

$ 1 g ------------\dfrac{100}{30.4} $

$ 14 g-------------\dfrac{100 \times 14}{30.4} $

$ \dfrac{doxide}{doxygen}=\dfrac{Moxide}{Moxygen}=\dfrac{\dfrac{1400}{30.4}}{32}=1.44 $