Tag: law of constant proportion - i

Questions Related to law of constant proportion - i

In an experiment, 2.4 g of iron oxide on reduction with hydrogen gave 1.68 g of iron. In another experiment, 2.9 g of iron oxide gave 2.09 g of iron on reduction. Which law is illustrated from the above data?

evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

  1. Law of constant proportions

  2. Law of multiple proportions

  3. Law of reciprocal proportions

  4. Law of conservation of mass

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Correct Option: A
Explanation:
In experiment 1,
$2.4\ g$ of iron oxide gives $1.68\ g$ iron on reduction with hydrogen.
$FeO \rightarrow Fe+O _2$
Percent of $Fe$ in $FeO$ is = $\frac{1.68}{2.4} \times 100=70$
Therefore ratio of $m _{Fe}:m _{O}::7:3$
In experiment 2:
$2.9\ g$ of iron oxide gives $2.09\ g$ iron on reduction.
Percent of $Fe$ in $FeO$ is = $\frac{2.09}{2.9} \times 100=72$

Therefore ratio of $m _{Fe}:m _{O} \approx 7:3$
When a given chemical compound contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation, it follows law of constant proportion.
option A is correct

A sample of calcium carbonate $(CaCO _{3})$ has the following percentage composition:
Ca = 40%; C = 12%; O = 48%.
If the law of constant proportions is true, then the weight of calcium in 4 g of a sample of calcium carbonate from another source will be:

evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

  1. 0.016 g

  2. 0.16 g

  3. 1.6 g

  4. 16 g

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Correct Option: C
Explanation:

In $100$ $g$ $CaCO _3$, $40$ $g$ $Ca$ is present.

In $4$ $g$ $CaCO _3$, Let $x$ $g$ $Ca$ be present
$\cfrac{x}{4}=\cfrac{40}{100}$
$\implies x=1.6$ $g$

A sample of calcium carbonate $\left( CaC{O} _3 \right)$ has the following percentage composition:
Ca = 40%; C = 12%; O = 48%.
If the law of constant proportions is true, then the weight of calcium in 4 g of a sample of calcium carbonate from another source will be ?

evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

  1. 0.016 g

  2. 0.16 g

  3. 1.6 g

  4. 16 g

Show answer
Correct Option: C
Explanation:

Calcium carbonate from any source contains 40% calcium. 

So each 1 g of calcium carbonate contains 0.4g of calcium.
Thus, for 4 g of calcium carbonate, the amount of calcium $=4\times 0.4=1.6g$

Different samples of water were found to contain hydrogen and oxygen in the ratio of 1 : 8. This shows the law of:

evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

  1. multiple proportions

  2. constant proportions

  3. reciprocal proportions

  4. conservation of mass

Show answer
Correct Option: B
Explanation:

Law of Constant proportion states that a chemical compound always contains same elements combined together in the same proportion by mass.

All samples of carbon dioxide contain carbon and oxygen in the mass ratio of $3 : 8$. This is in agreement with the law of :

evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

  1. conservation of mass

  2. constant proportion

  3. multiple proportions

  4. gaseous volumes

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Correct Option: B
Explanation:

LAW OF CONSTANT OR DEFINITE PROPORTION : It was given by Proust.
It states that all chemical compounds are found to have constant composition irrespective of their method of preparation or sources.
THE LAW OF MULTIPLE PROPORTION : It was given by Dalton.
It states that when one element combines with the other element to form two or more different compounds, the mass of one element which combines with a constant mass of the other bear a simple ratio to one another.

Law of constant composition is also called as the law of :

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  1. Conservation of mass

  2. Conservation of energy

  3. Multiple proportion

  4. Definite proportion

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Correct Option: D
Explanation:

Law of constant composition is also called as the law of Definite proportion which says that the law of constant composition is a chemistry law which states samples of a pure compound always contain the same elements in the same mass proportion.

When hydrogen and oxygen combine to form water, they form:

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  1. an unstable compound

  2. a stable mixture

  3. an unstable mixture

  4. an extremely stable compound

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Correct Option: D
Explanation:

When hydrogen and oxygen combine to form water, they form water an extremely stable compound. We can say water is a stable compound because tremendous energy is released is a signal that hydrogen and oxygen are very eager to become water or in another way it is very hard to break water molecules apart into its components.

$2H _2+O _2\longrightarrow 2H _2O$

In ammonia, nitrogen and hydrogen always combine in $14:3$ ratio by mass. This is in agreement with :

evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

  1. Law of conservation of mass

  2. Law of definite proportion

  3. Law of multiple proportion

  4. Law of combining volume

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Correct Option: B
Explanation:

Law of definite proportion states that elements always combine in the definite ratio by mass. So it is in agreement with the law of definite proportion.

Law of definite proportion does not apply to nitrogen oxide because:

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  1. Atomic weight of nitrogen is not conserved

  2. Molecular weight of nitrogen is variable

  3. Equivalent weight of nitrogen is variable

  4. Atomic weight of oxygen is variable

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Correct Option: C
Explanation:

Nitrogen forms multiple compounds with oxygen. Hence, we cannot apply the law of definite proportion to nitrogen oxide.

The ratio of mass of nitrogen and oxygen in nitric oxide is in :

evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

  1. $7:16$

  2. $1:8$

  3. $7:8$

  4. $7:15$

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Correct Option: C
Explanation:

Formula of Nitric oxide is NO. Mass of nitrogen in NO is 14 g. Mass of oxygen is 16. Therefore ratio is $14:16$ i.e $7:8$.