Core Ideas of Chemistry

Which of the following statements about a compound is incorrect?

• (a) A molecule of a compound has atoms of different elements.

• (b) A compound cannot be separated into its constituent elements by physical methods of separation.

• (c) A compound retains the physical properties of its constituent elements.

• (d) The ratio of atoms of different elements in a compound is fixed

Tags

NGSS.MS-PS1-1

16 g of oxygen has same number of molecules as in [atomic mass of O=16, C=12, N=14, H=1]

• (a) 16 g of CO

• (b) 28 g of N₂

• (c) 14 g of N₂

• (d) 1.0 g of H₂

Tags

NGSS.HS-PS1-7

One atomic mass unit (amu) is closest to the mass of:

• The oxygen-16 nucleus

• The carbon-12 nucleus

• 6.022 x 10²³ atoms of hydrogen

• One proton

The unit of amount of substance is:

• ampere

• second

• mole

• kilogram

The law of multiple proportions was proposed by __________

Law of constant proportion states that

• matter can neither be created nor destroyed

• equal volumes of gases at the same temperature and pressure should contain equal number of molecules.

• a given compound always contains exactly the same proportion of elements by weight.

• if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in the ratio of small whole numbers

How much copper can be obtained from 100 g of copper sulphate (CuS0₄)? [atomic mass of Cu=63.5, S=32, O=16]

• 63.5g

• 39.8g

• 159.5g

• 35.8g

Tags

NGSS.HS-PS1-2

NGSS.HS-PS1-7

What is the concentration of sugar (C₁₂H₂₂O₁₁) in mol L ^-1 if its 20 g are dissolved in enough water to make a final volume up to 2 L?

• 0.058 mol/ L

• 10 mol /L

• 0.0058 mol / L

• 0.029 mol/L

Chlorine is prepared in the laboratory by treating manganese dioxide (Mn02) with aqueous hydrochloric acid according to the reaction

4HCI_(aq) + MnO_2(s) → 2H₂O_(I) + MnCI_2(aq) + Cl_2(g)

How many grams of HCI react with 5.0 g of manganese dioxide? [atomic mass of Mn=55, O=16, H=1, Cl=35.5u]

• 8.4g

• 9.2g

• 5.4g

• 10.5g

Tags

NGSS.HS-PS1-2

NGSS.HS-PS1-7