CHEM 1113- Ch. 0 Homework

A certain ore is 34.4% nickel by mass. How many kilograms of this ore would you need to dig up to have 45.0g of nickel?

0.131 kg There is 34.4g of nickel per 100g ore. Use that relationship to convert between the mass of nickel and the mass of ore. 45.0g Ni × (100g ore/34.4g Ni) = 131g ore Finally, convert from grams to kilograms. 131g × (1 kg/1000g) = 0.131 kg

How many grams of salt are needed to make 471g of salt water that is 36.5% salt by mass?

172 grams salt

A mixture is made by combining 1.131.13 lb of salt and 5.155.15 lb of water. What is the percentage of salt (by mass) in this mixture?

18% Percent composition is determined by the expression %composition=(mass of component)/(total mass)×100% Divide the mass of the salt by the total mass of the salt and water. % composition=(1.13 lb)/(1.13 lb+5.15 lb)×100%=18.0%

Find the weighted average of these values. 4.00 = 75.0% 5.00 = 15.0% 6.00 = 10.0%

4.35

In a particular class, exams are worth 50% of the overall grade, quizzes are worth 30% of the overall grade, homework is worth 15% of the overall grade, and class participation is worth 5% of the overall grade. A particular student has earned an average score of 82.7% on the exams, 71.4% on the quizzes, 90.0% on the homework, and 100.0% on class participation. What is this student's overall grade in the course? (Report the answer with one digit after the decimal point.)

81.3%

The human body contains many elements from the periodic table. It is mostly composed of oxygen and carbon, but trace elements also have a significant role. The table gives the mass, in kilograms, of some elements found in the human body, based on a 70.0 kg person. potassium = 0.25 kg phosphorus = 0.78 1) Potassium makes up what fraction of the mass of the human body? 2) Potassium makes up what percentage of the mass of the human body? 3) What is the mass of phosphorus in a 49 kg person?

A) 0.0036 B) 0.36% C) 0.55 kg