Tutor profile: Alana R.

James and Jim decided to buy a pizza for lunch. James had 1/4 of the pizza and Jim had 1/2 of the pizza. How much of the pizza is left?

1/4 + 1/2 (need common denominator of 4, therefore we multiple 1/2 by 2/2) 1/4 +2/4 = 3/4 (with a common denominator the numerator can be added) 3/4 of the pizza was eaten. However, we need to find how much of the pizza is left. 1 - 3/4 (this is how much of the pizza is left since we started with 1 pizza. we need a common denominator, so we multiply 1 by 4/4) 4/4 - 3/4 = 1/4 There is 1/4 pizza left over from lunch.

The pH of coca cola is approximately 2.37. What is the concentration of protons (H+) in a glass of coke?

pH = 2.37 = - log ([H+]) [H+] = 10^-pH = 10^-2.37 = 0.00427 M The concentration of protons in a glass of coke is 0.00427 M.

Jessie has sore throat and would like to make a salt water solution to help it. The recommended concentration for a salt water solution is 0.11 M NaCl. If Jessie wants to make 200 mL of this solution, what weight of salt does she need in grams?

0.11 M = x mol/ 0.2 L x= 0.022 mol g = 0.022 mol * 58.44 g/mol = 1.3 grams Jessie needs 1.3 grams in 200 mL of water to create the recommended salt water solution.