A pure substance which contains only one type of atom is called?? 

Round up the following upto three significant figures: (iii) 0.04597

In three moles of ethane ($C_2H_6$), calculate the following: (iii) Number of molecules of ethane.

Chlorine is prepared in the laboratory by treating manganese dioxide ($MnO_2$) with aqueous hydrochloric acid according to the reaction
$4 HCl (aq) + MnO_2(s) \rightarrow 2H_2O (l) + MnCl_2(aq) + Cl_2 (g)$
How many grams of HCl react with 5.0 g of manganese dioxide?

How many significant figures are present in the following? (iii) 5005

Round up the following upto three significant figures: (ii) 10.4107

How are 0.50 mol $Na_2CO_3$ and 0.50 M $Na_2CO_3$ different?

How many significant figures are present in the following? (iv) 126,000

Which of the following is a homogeneous mixture?

Identify which of the following properties is extensive .

(a) volume

(b) temperature

(c) boiling point

Use the data given in the following table to calculate the molar mass of naturally occuring argon isotopes:
Isotope Isotopic molar mass Abundance
$^{36}Ar$ 35.96755 g $mol^{-1}$ 0.337%
$^{38}Ar$ 37.96272 g $mol^{-1}$ 0.063%
$^{40}Ar$ 39.9624 g $mol^{-1}$ 99.600%

Express the following in the scientific notation: (iii) 8008

What is the concentration of sugar ($C_{12}H_{22}O_{11}$) in $mol L^{-1}$ if its 20 g are dissolved in enough water to make a final volume up to 2L?

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 (iii) molecular formula.

If the density of methanol is 0.793 kg $L^{-1}$, what is its volume needed for making 2.5 L of its 0.25 M solution?

Fill in the blanks in the following conversions: (i) 1 km = ...................... mm = ...................... pm

The following data are obtained when dinitrogen and dioxygen react together to form different compounds:
Mass of dinitrogen Mass of dioxygen
(i) 14 g 16 g
(ii) 14 g 32 g
(iii) 28 g 32 g
(iv) 28 g 80 g
(a) Which law of chemical combination is obeyed by the above experimental data? Give its statement.

What is the SI unit of mass? How is it defined?

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 (ii) molar mass of the gas

Calculate the number of atoms in each of the following (i) 52 moles of Ar