20 quastions-quantative chem and science skills

Question 1

state the law of conservation of mass

Answer 1

the mass of reactants is always equal to the total mass of products

Question 2

calculate the relative formula mass of calcium carbonate CaC03

Answer 2

40+12+(16x3)=100

Question 3

why must symbol equations balance

Answer 3

because no atoms are lost of made since the products are made from exactly the same atoms as the reactants

Question 4

when metals form metal oxide ,why does the mass increase

Answer 4

because oxygen atoms have chemically bonded to the metal atoms

Question 5

calculate the relative formula mass of water

Answer 5

h20=(2x1)+16=18

Question 6

what does the state symbol aq stand for

Answer 6

aqueous (dissolved in water)

Question 7

whats avogadros number (number of atoms in a mole)

Answer 7

6.02 x 10^23

Question 8

whats the equation that links moles mass and mr

Answer 8

mass=mr X moles

Question 8

69g of sodium reacts with sodium chlorine to produce sodium chloride 2na+Cl2->2NaCL. calculate the moles of sodium present

Answer 8

69/23=3 moles of Na

Question 9

calculate the moles of chlorine requireed to react exactly woth sodium in 2na+Cl2->2NaCL.

Answer 9

from the eqation you get NA:CL ratio is 2:1 but we have 3 moles not 2 so 3;1.5 is required

Question 10

whats the equation we use to find the concentration of a liquid

Answer 10

conc=mass or moles/volume in dm

Question 11

whatre the units of concentration

Answer 11

g/dm^3 or moles/dm^3

Question 12

1.5 moles of solute are dissolced in 1 dm of solvent,whats the concentration of solution formed

Answer 12

1,5 moles.1.00 dm=1.50 mol/dm cubed

Question 13

2 g of solute are dissolved in 2 dm of solvent,whats the concentration of solution formed

Answer 13

2/2=1 g/dm cubed

Question 14

0.2 moles of solute are dissolved in 500cm of solvent whats the concentration of the solution formed

Answer 14

0.2/0.5dm=0.4 mol/dm cubed

Question 15

why might actual yields of reactions be less than the theoretical yield of a reaction

Answer 15

some product is lost when its seperated from the reaction, if reactions are reversable when it may not complete and some reactants react in diff ways than the expected reaction

Question 16

a reaction has a theoretical yield of 13g but an actual yield of 8.5g whats the percentage yield of this reaction

Answer 16

(8.5/13)x100=65.4%

Question 17

why are reactions that have high atom economy good for the environment

Answer 17

they produce less waste that could damage the environment like co2 and global warming

Question 18

the equation to form ammonia is NH3, is: N2 + 3H2 → 2NH3, whats the percentage atom economy of this reaction

Answer 18

100 percent cayse theres only 1 product

Question 19

whats a limiting reactant

Answer 19

A reaction finishes when one of the reactants is all used up. The
other reactant has nothing left to react with, so some of it is left over:
the reactant that is all used up is called the limiting reactant