Considering the definition of percentage by mass, the sample of pure lithium nitrate contains 7.99% lithium by mass.
<h3>Definition of percentage by mass</h3>
The percentage by mass expresses the concentration and indicates the amount of mass of solute present in 100 grams of solution.
In other words, the percentage by mass of a component of the solution is defined as the ratio of the mass of the solute to the mass of the solution, expressed as a percentage.
The percentage by mass is calculated as the mass of the solute divided by the mass of the solution, the result of which is multiplied by 100 to give a percentage. This is:

<h3>This case</h3>
Because percent by mass indicates the ratio of solute to solution based on mass, if the sample has twice the mass of the first sample, the ratio remains constant.
So the percentage by mass is the same.
That is, the sample of pure lithium nitrate contains 7.99% lithium by mass.
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it is a disease, commonly found in young children.
In determining safe speed of a vessel we must consider visibility, traffic density etc.
<h3>What is safe speed?</h3>
The safe speed of a vessel is the maximum speed the vessel can be operated to avoid hazards such as collision, damage of vessel, etc.
<h3>Factors considered when determining safe speed of vessels</h3>
In determining safe speed of a vessel we must consider the following factors such as;
- Weather condition, eg visibility
- Traffic density,
- Background light at night, etc
Thus, in determining safe speed of a vessel we must consider visibility, traffic density etc.
Learn more about safe speed here: brainly.com/question/6504879
well first he would have to work intervals at a time for example 15 min study intervals then snack break but only brain foods to help his memory then repeat the proceed until desired time
plz mark brainliest