Law of Conservation of Mass

Q.

Estimate the mass of urea (NH₂CONH₂) required in making 2.5 kg of 0.25 molal aqueous solution.

Q. What are molecules?

Q.

What is the molar mass of acetic acid?

Q.

Copper sulphate reacts with sodium hydroxide to form a blue precipitate of copper hydroxide and sodium sulphate. In an experiment, 15.95 g of copper sulphate reacted with 8.0 g of sodium hydroxide to form 9.75 g of copper hydroxide and 14.2 g of sodium sulphate. Which law of chemical combination is illustrated by this data?

Q. What is synthesis reaction? What kind of chemical reaction is synthesis? Support your answer by an example.

Q.

Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?

Q. Question 49 (c)
An element X which is a yellow solid at room temperature shows catenation and allotropy. X forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are the major air pollutants

Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals.

Q.

What is the molar mass of copper $\left(\mathrm{II}\right)$ chloride?

Q. Why is compound a pure substance ?

Q.

In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g of water, and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass.

sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water.

Q.

Write the formula of Aluminum sulfate? Calculate its formula unit mass.

Q.

Explain the law of conservation of mass

Q.

Name the scientist who gave:

(a) Law of conservation of mass.

(b) Law of constant proportions.

Q.

The mass of an atom of oxygen is $16.0\mathrm{u}$ express in Kg.

Q.

What is the molar mass of barium chloride $\left({\mathrm{BaCl}}_2\right)$ ?

Q.

State the law of conservation of mass. Give one example to illustrate this law.

Q.

Question 44
Fill in the blanks

(a) In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called ___.

(b) A group of atoms carrying a fixed charge on them is called ___.

(c) The formula unit mass of $C{a}_3(P{O}_4{)}_2$ is ____.

(d) Formula of sodium carbonate is ___ and that of ammonium sulphate is ____.

Q.

Hydrogen and oxygen combine in the ratio of ________ to form water.

1. 1:2

2. 8:1

3. 2:1

4. 1:8

Q. Which of the following statements is true about the law of conservation of mass?

1. In a chemical reaction, efforts should be made to preserve rare elements without changing them.
2. Matter can be created and destroyed but does not change forms.
3. In a chemical reaction, matter is not created or destroyed, but is conserved.
4. In a chemical reaction, the final mass of the products is always greater than the starting mass of the reactants.

Q.

Two substances, A and B were made to react to form a third substance, ${\mathrm{A}}_2\mathrm{B}$ according to the following reaction $2\mathrm{A}+\mathrm{B}\to {\mathrm{A}}_2\mathrm{B}$ which of the following statements concerning this reaction are incorrect? (i) The product ${\mathrm{A}}_2\mathrm{B}$ shows the properties of substances A and B (ii) The product will always have a fixed composition (iii) The product so formed cannot be classified as a compound (iv) The product so formed is an element.

1. (i), (ii) and (iii)

2. (ii), (iii) and (iv)

3. (i), (iii) and (iv)

4. (ii) and (iv) only

Q.

With the help of a labelled diagram, describe the preparation of oxygen in the laboratory. Provide the balances equation

Q.

Mass is not conserved in a chemical reaction.

1. True

2. False

Q.

Calculate the amount of mercury obtained by the decomposition of 2.16 kg of mercuric oxide.

Q.

All chemical equations must be balanced to complete with ________ [Avogadros Law/ Law of conservation of matter/ Lussacs Law].

Q. Fe +S =Fes. Calculate the mass in g of iron sulphide formed when 28g of iron combines with 16g of sulphur.

Q. Question 12
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

Q.

Calculate the mass of nitrogen which contain the same number of molecules as are contained in 4.4 grams of carbon dioxide.

Q. Question 10 (j)
Classify the following into elements, compounds and mixtures.
j. Soap

Q.

The law of conservation of mass was given by:

1. Dalton

2. Proust

3. Lavoisier

4. Berzelius

Q. Ca+Cl2 gives CaCl2. Calculate the mass of chlorine left unreacted when 80g of calcium reacts with 150g of chlorine to form 222g of calcium chloride.