Practice free Some Basic Concepts in Chemistry (Chemistry) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
The concept of atoms being fundamental building blocks of matter, while revived by Dalton in the 19th century, originated from:
The NCERT states, 'The existence of atoms has been proposed since the time of early Indian and Greek philosophers (400 B.C.) who were of the view that atoms are the fundamental building blocks of matter.'
Which of the following aspects of chemical behavior cannot be explained by the 'Daltonian model of atom'?
The text explicitly states: 'For example, questions like why two or more atoms combine to form molecules, why some elements are metals while others are non-metals, why elements like helium and argon are not reactive but elements like the halogens are reactive, find simple explanation from the electronic configuration. These questions have no answer in the Daltonian model of atom.'
The right option for the mass of CO₂ produced by heating 20 g of 20% pure limestone is (Atomic mass of Ca = 40):
$$\text{CaCO}_3 \xrightarrow{1200\,\text{K}} \text{CaO} + \text{CO}_2$$
Pure CaCO₃ = 4 g $\Rightarrow$ moles = 0.04. CO₂ mass = $0.04 \times 44 = 1.76\ \text{g}$.
Which amongst the following options is the correct graphical representation of Boyle's Law?
Boyle: $PV =$ const $\Rightarrow P = (\text{const})/V$, so $P$ vs $1/V$ is a straight line through origin. With higher T the slope (= nRT) is larger.
1 gram of sodium hydroxide was treated with 25 mL of $0.75$ M HCl solution, the mass of sodium hydroxide left unreacted is equal to:
25 mmol NaOH, 18.75 mmol HCl. Remaining NaOH = 6.25 mmol $\times$ 40 $=$ 250 mg.
The highest number of helium atoms is in
Atoms: (A) 0.1 mol $\approx 6\times 10^{22}$; (B) $4N_A$; (C) 1 atom; (D) $N_A$. (B) is the largest.
A compound X contains 32% of A, 20% of B and remaining percentage of C. Then, the empirical formula of X is:
(Given atomic masses of $A = 64$; $B = 40$; $C = 32$ u)
Moles: $A = 32/64 = 0.5$; $B = 20/40 = 0.5$; $C = 48/32 = 1.5$. Ratio $1:1:3$ → $ABC_3$.
Dalton's Atomic theory could not explain which of the following?
Dalton's theory explained the laws of conservation of mass, constant and multiple proportions, but could not explain Gay-Lussac's law of gaseous volumes.
Among the following, choose the ones with equal number of atoms. A. 212 g of $\text{Na}_2\text{CO}_3$ [molar mass 106 g], B. 248 g of $\text{Na}_2\text{O}$ [molar mass 62 g], C. 240 g of NaOH [molar mass 40 g], D. 12 g of $\text{H}_2$ [molar mass 2 g], E. 220 g of $\text{CO}_2$ [molar mass 44 g]. Choose the correct answer:
A: 2 mol × 6 atoms = 12 $N_A$; B: 4 mol × 3 = 12 $N_A$; C: 6 mol × 3 = 18 $N_A$; D: 6 mol × 2 = 12 $N_A$; E: 5 mol × 3 = 15 $N_A$. Equal (12 $N_A$): A, B and D.
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