0.40g
0.80g
4.00g
8.00g
Correct answer is C
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Relative molecular mass of NaOH = 23 + 16 + 1 = 40smol-1
2 * 23g of sodium react with water to produce
2 * 40g of NaOH
∴ 2.3g of sodium will react with water to produce
(2.3 * 40 * 2)/(23 * 2) = 4.00g
lower the melting point of the ice
increase the density of the ice
make the ice impure
raise the melting point of the ice
Correct answer is A
The presence of impurities in a substance lowers the melting point. Salt is added on icy roads to cause the ice to melt on time.
crystallization
hydrolysis
chromatography
sublimation
Correct answer is C
The chlorophyll from the green leaves of plant being a mixture can be separated by Chromatography into its different components. Chromatography has to do with the separation of coloured components. chromatography is used in industrial processes to purify materials, test trace amounts of contaminants, isolate chiral compounds, and quality control test products
What weight of NaCl is needed to make 2.0 dm3 of a 1.5M solution?
[Na = 23, Cl = 35.5]
116 g
175 g
87 g
58 g
Correct answer is B
Molar mass of Nacl = 23 + 35.5 = 58.5 g/mol
Number of moles of Nacl = conc. in mol/dm3
x vol. in dm3
= 1.5 * 2.0 = 3.0 moles
1 mole of NaCl has a weight of 58.5 * 3
= 175.5g
Smog usually occurs over cities which
burn a lot of fossil fuels
have very few plants
are surrounded by water
are overpopulated
Correct answer is A
No explanation has been provided for this answer.