Tag: chemistry

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Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula water of crystallisation

Given:
Mass of beaker is X g
Mass of beaker + mixture is Y g
Mass of washed and dried sand is Z g
Find the percentage of sand in the mixture.

  1. $\frac{Y-X}{100}\times Z$
  2. $\frac{Y-X}{Z}\times 100$
  3. $\frac{Z}{Y-X}\times 100$
  4. $\frac{100}{Y-X}\times Z$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Mass of mixture=$Y-X$

Percentage of sand= $\frac{weight   of   sand}{weight   of   mixture}\times 100$
                                 =$\frac{Z}{Y-X}\times100$

Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula water of crystallisation

If the % composition of a 'x' component is 35%, find the mass of the dried 'x' component in 100g? mixture + beaker = 50 g, mass of beaker = 23 g

  1. 15.5 g

  2. 9.45 g

  3. 35.5 g

  4. 13.4 g
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

mass of beaker $= 23g$
mass of mix + beaker$ = 50g$
mass of mixture $= 50 - 23 = 27g$
$\%$ composition of mixture $= 35\%$
Mass of the x component $= 35 \times  \dfrac{27}{100} = 9.45g$

Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula water of crystallisation

The mass of a sand and powdered mixture along with a beaker is 56 g. If the mass of the dried mixture is 20 g, find the % composition of the mixture in 100 g?
(weight of beaker = 20 g).

  1. 20%

  2. 36%

  3. 55%

  4. 60%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Mass of beaker = 20 g
Mass of mixture + beaker = 56 g
Mass of mixture = 56 - 20 = 36 g
Mass of washed and dried sand = 20 g
100 g of mixture contains $= \dfrac{20}{36} \times 100 = 55$% of sand

Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula water of crystallisation

Calculate the % composition of Carbon in $CO _2$. Molar mass is 44.01.

  1. 40%

  2. 67%

  3. 30%

  4. 27%
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Molar mass of compound:
Mass due to carbon:   12.01 g/mol
Total molar mass $= 12.01 + 2(16.00) = 44.01g/mol$             ($CO _2$ has two $O _2$ atoms)
Percent composition of carbon: $12.01/44.01 \times 100 = 27.28$%

Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula water of crystallisation

If the % composition of Cl in HCl is 46%, what is the mass of Cl in HCl?

  1. 13.3 g

  2. 66 g

  3. 25 g

  4. 16.76 g
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\%$ $ composition =\cfrac{Mass \quad of\quad an \quad element.}{Total \quad mass \quad of\quad compound.}$

$Total \quad mass\quad of\quad HCl=1+35.5 g=36.5g$
$\therefore$ $\cfrac{46}{100}=\cfrac{mass\quad of\quad Cl}{36.5}\ mass\quad of\quad Cl=16.76g$

Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula water of crystallisation

Mass of beaker=20 g
Mass of beaker+mixture=50 g
Mass of washed and dried sand=5 g
Find the percentage of sand in the mixture.

  1. 16.67%

  2. 20%

  3. 25%

  4. 30%
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Mass of mixture=$50 g-20 g=30 g$

Mass of washed and dried sand in the mixture=$5g$
Percentage=$\frac{5}{30}\times 100$
                   =16.67%


Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula water of crystallisation

Mass of beaker=10g
Mass of mixture+beaker=25g
Mixture contains 30% sand. Find the weight of sand.

  1. 5 g

  2. 4.5 g

  3. 3 g

  4. 3.5 g
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mass of mixture=$25g-10g=15g$

Percentage of sand=30%=$\frac{Mass  of  sand}{Mass  of  mixture}$
 Mass of sand =$0.3\times15g=4.5 g$

Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula

Which of the following compound represents an alkane?

  1. ${C} _{5}{H} _{8}$
  2. ${C} _{7}{H} _{16}$
  3. ${C} _{8}{H} _{6}$
  4. ${C} _{9}{H} _{10}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Alkanes have general molecular formula is $C _nH _{2n+2}$


$\therefore C _7H _{16}$ is Alkane.

Hence, the correct option is $\text{B}$

Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula

The number of $g$ molecules of oxygen in $6.023\times 10^{24} \ CO$ molecules is ________________.

  1. $1\ g$ molecule
  2. $0.5\ g$ molecule
  3. $5\ g$ molecules
  4. $10\ g$ molecules
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$1$ mole of $CO=6.023\times 10^{23}$ molecules

$x$ mole of $CO=6.023\times 10^{24}$ molecules
$\therefore x=10$ moles $=10\ g$ molecules
$CO=1$ oxygen atom
$\therefore$ Oxygen molecules $=\dfrac{10}{2}$
$=5\ g$ molecules 
Option $C$ is correct.