Because they're not confident enough to confirm it's indeed true but they will support it for they believe it's correct.
Answer: option A) Mixtures may be composed of two or more elements, two or more compounds, or a combination of both.
Explanation:
A mixture is a combination of two or more substances mixed together and can be separated by physical methods.
A combination of two elements or compounds will yield chemical compounds NOT a mixture.
Thus, option A is false statement
Answer:
400 mL of 4% salt solution and 600 mL of 16% salt solution need to be mixed
Explanation:
Let's assume concentration of brine salt solutions are in %(w/v) unit.
Final mixture has a concentration of 11.2% salt and volume of 1 L or 1000 mL
Hence, amount of salt in final mixture = 
Suppose x mL of 4% salt solution and (1000-x) mL of 16% salt solution need to be mixed to get final mixture
So, amount of salt in x mL of 4% salt solution = 
amount of salt in x mL of 16% salt solution =
Hence, 
or, 
So, 400 mL of 4% salt solution and 600 mL of 16% salt solution need to be mixed
Answer:
229%
Explanation:
The equation of the reaction is;
4Al(s) + 3O2(g) ----> 2Al2O3(s)
We must first determine the limiting reactant;
Number of moles of Al2O3 produced = mass/molar mass = 72.4g/101.96 g/mol = 0.71 moles
For Al
Number of moles reacted = mass/molar mass = 49.2g/27 g/mol = 1.8 moles
If 4 moles of Al yields 0.71 moles of Al2O3
1.8 moles of Al will yield 1.8 × 0.71/4 = 0.32 moles of Al2O3
For O2
Number of moles reacted = mass/molar mass = 42.6g/32g/mol = 1.33 moles
If 3 moles of O2 yields 0.71 moles of Al2O3
1.33 moles of O2 will yield 1.33 × 0.71/3 = 0.31 moles of Al2O3
Oxygen is the limiting reactant.
% yield = actual yield/ theoretical yield × 100/1
% yield = 0.71 moles/0.31 moles × 100
% yield = 229%
