Class 11 Chemistry - Chapter Some Basic Concepts of Chemistry NCERT Solutions | Round up the following upto three signif
Round up the following upto three significant figures:
(i) 34.216
(ii) 10.4107
(iii) 0.04597
(iv) 2808
Rounding off a number means that the digits which are not significant have to be dropped.The rules are as follows:
- if the digit to be dropped is more than 5, then add 1 to the preceding significant figure.For eg in the number 11.06, the digit to be dropped is 6.Therefore the preceding digit 0 is increased by one & the final result is 11.1.
- if the digit to be dropped is less than 5,then it is deleted as such without bringing any change in the preceding significant figure.For eg 43.123 is to reported upto four significant figures,then the last digit 3 is dropped & the final answer is 43.12.
- if the digit to be dropped is 5 then the preceding significant digit in the number may be left unchanged if it is even & may be increased by 1 in case if it is odd.Eg 1.6145, if reported upto four significant figures will become 1.614 after rounding off. Similarly 1.6175 will become 1.618.
- if during rounding off, more than one digit is to be dropped form a particular number, then they are dropped on at a time by following the above rules.
(i) 34.2
(ii) 10.4
(iii) 0.0460
(iv) 2810
More Questions From Class 11 Chemistry - Chapter Some Basic Concepts of Chemistry
- Q:-
Calculate the amount of carbon dioxide that could be produced when
(i) 1 mole of carbon is burnt in air.
(ii) 1 mole of carbon is burnt in 16 g of dioxygen.
(iii) 2 moles of carbon are burnt in 16 g of dioxygen.
- Q:-
In a reaction A + B2 → AB2 Identify the limiting reagent, if any, in the following reaction mixtures.
(i) 300 atoms of A + 200 molecules of B
(ii) 2 mol A + 3 mol B
(iii) 100 atoms of A + 100 molecules of B
(iv) 5 mol A + 2.5 mol B
(v) 2.5 mol A + 5 mol B
- Q:-
Which one of the following will have largest number of atoms?
(i) 1 g Au (s)
(ii) 1 g Na (s)
(iii) 1 g Li (s)
(iv) 1 g of Cl2(g)
- Q:-
Chlorine is prepared in the laboratory by treating manganese dioxide (MnO2) with aqueous hydrochloric acid according to the reaction
4HCl(aq) + MnO2(s) → 2H2O(l) + MnCl2(aq) + Cl2(g)
How many grams of HCl react with 5.0 g of manganese dioxide?
- Q:-
Determine the empirical formula of an oxide of iron which has 69.9% iron and 30.1% dioxygen by mass.
- Q:-
A sample of drinking water was found to be severely contaminated with chloroform, CHCl3, supposed to be carcinogenic in nature. The level of contamination was 15 ppm (by mass).
(i) Express this in percent by mass.
(ii) Determine the molality of chloroform in the water sample.
- Q:-
Calcium carbonate reacts with aqueous HCl to give CaCl2 and CO2 according to the reaction,
CaCO3(s) + 2 HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
What mass of CaCO3 is required to react completely with 25 mL of 0.75 M HCl?
- Q:-
Calculate the mass of sodium acetate (CH3COONa) required to make 500 mL of 0.375 molar aqueous solution. Molar mass of sodium acetate is 82.0245 g mol–1
- Q:-
A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide, 0.690 g of water and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Calculate
(i) empirical formula,
(ii) molar mass of the gas, and
(iii) molecular formula.
- Q:-
How many significant figures are present in the following?
(i) 0.0025
(ii) 208
(iii) 5005
(iv) 126,000
(v) 500.0
(vi) 2.0034
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- Q:-
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- Q:-
What are hybridisation states of each carbon atom in the following compounds ?
(i) CH2=C=O,
(ii) CH3CH=CH2,
(iii) (CH3)2CO,
(iv) CH2=CHCN,
(v) C6H6
- Q:-
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- Q:-
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- Q:-
Assign oxidation number to the underlined elements in each of the following species:
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(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
(e) CaO2
(f) NaBH4
(g) H2S2O7
(h) KAl(SO4)2.12 H2O
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Explain the formation of a chemical bond.
- Q:-
Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only. - Q:-
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure? - Q:-
Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
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- Q:-
Does the number of moles of reaction products increase, decrease or remain same when each of the following equilibria is subjected to a decrease in pressure by increasing the volume?
(a) PCl5 (g) ↔ PCl3 (g) + Cl2 (g)
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1 Comment(s) on this Question
Could not under 2810 , rounding off.
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