SC9b Conservation of Mass

Question 1

9.5 Explain the law of conservation of mass applied to a closed system including a precipitation reaction in a closed flask and a non-enclosed system including a reaction in an open flask that takes in or gives out a gas

Question 2

9.6 Calculate masses of reactants and products from balanced equations, given the mass of one substance

Question 3

9.7 Calculate the concentration of solutions in g dm–3​

Question 4

what is conservation of mass?

Answer 4

Mass is never lost or gained in chemical reactions. the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning.​

Question 5

what is a closed system?

Answer 5

no new substances are added or removed​ in a chemical reaction

Question 6

what is a non closed system?

Answer 6

new substances are released like gas which changes the mas, if there was a lid on this reaction the mass would stay the same

Question 7

Calculate the mass of water obtained when 16 tonnes of hydrogen react with oxygen.​

2H2 + O2 → 2H2O​

Answer 7

Mr H2 = 2 H2O = 18​
x big numbers 2 x 2 = 4 2 x 18 = 36​
Ratios 4 : 36​
so 16 : answer = 144

Question 8

solution mass =

Answer 8

Solute mass + Solvent mass

Question 9

Concentration =

Answer 9

mass of solute in g / volume of solution in g dm3

Question 10

cm3 to dm3

Answer 10

divide by 1000

Question 11

calculate the concentration of 5g of Lithium in 2dm3 of water

Answer 11

2.5g dm3

Question 12

Calculate the maximum mass of magnesium oxide that could be formed by reacting 1.56g of magnesium with excess oxygen.​
2Mg + O2 → 2MgO (3 marks)​

Answer 12

2 x 24 2 x (24 + 16)
=48 =80
1.56 2.6
answer = 2.6g