Chocolate Cake

An aqueous solution of sodium chloride,NaCl , is made by dissolving 1.01 grams of sodium chloride in sufficient water in a 50.0 mL volumetric flask, and then adding enough water to fill the flask to the mark. What is the weight/volume percentage of sodium chloride in the solution? Weight/volume percentage =           %

Assume that your empty crucible weighs 15.98 g, and the crucible plus the sodium bicarbonate sample weighs 18.56 g. After the first heating, your crucible and contents weighs 17.51 g. After the second heating, your crucible and contents weighs 17.50 g. Answer the following questions based on this information.

NHẠNO3 MgSO4 [1] Mass of salt (g) 1.968 1.981 [2] Volume of DI water (mL) 50.0 50.0 0.039 0.0396 Mass of DI water (g) [3] Temperature of DI water (°C) 22.5 22.5 [4] Temperature of mixture after dissolution (°C) 19.5 27.1 3 4.6 Temperature difference (°C) [5] Total mass in reaction (g) [6] Enthalpy of solution AHsolution (cal/mol)

-1 A geochemist measures the concentration of salt dissolved in Lake Parsons and finds a concentration of 4.27 g·L *. The geochemist also measures the concentration of salt in several nearby non-isolated lakes, and finds an average concentration of 2.6 g-L. Assuming the salt concentration in Lake Parsons before it became isolated was equal to the average salt concentration in nearby non-isolated lakes, calculate the percentage of Lake Parsons which has evaporated since it became isolated. Be sure your answer has the correct number of significant digits.

A pool cleaning solution is mixed from three different bottles of solution. The first bottle contains a solution that is 25% chlorine, the second bottle contains a solution that is 58% chlorine, and the other bottle contains a solution that is 44% chlorine. There is twice as much of the 25% chlorine solution as there is the 44% chlorine solution. The final mixture consists of 154 ounces of a solution that is 37.4% chlorine. How many ounces of the bottle that contained 25% chlorine were used in the final solution? (round your answer to the nearest tenth) record 7 O O O 79.3 ounces 39.7 ounces 59.5 ounces O 35.0 ounces 2 W S 3 E D $ 4 R F 5 F6 T G Search 6 B Y FB & 7 H U N F9 * 8 J 1 F10 M ( 9 K O ) O ( F12 L P Prt Sc : + [ = 1 Backspace 40 D 3:41 P 6/15/202 7

A sunscreen preparation contains 2.50% by mass benzyl salicylate. If a tube contains 4.0 ounces of sunscreen, determine how many kilograms of benzyl salicylate are needed to manufacture 325 tubes of sunscreen. Conversion: 2.205 lb= 1 kg.  16.0 oz = 1 lb

H8.

A sunscreen preparation contains 2.50% by mass benzyl salicylate (2.50g benzyl salicylate/100g sunscreen). If a tube contains 4.00 ounces of sunscreen, how many kilograms of benzyl salicylate are needed to manufacture 325 tubes of sunscreen? (16 oz = 1 lb; 454g = 1 lb).

Pipet (1.0x10^1) mL of a sample solution into a 250.00 mL volumetric flask and dilute to the mark with distilled water. Then, pipet 2 mL of this diluted solution into a 50.00 mL volumetric flask and dilute to the mark with distilled water. What is the dilution factor of the final solution? (Note: keep one decimal in your answer.)

What volume of 95.0% alcohol by weight (density: 0.809g/cm^3) must be used to prepare150 cm^3 of 30.0% alcohol by weight (density: 0.957g/cm^3)

An aqueous solution of sodium nitrate, NaNO3 , is made by dissolving 26.7 grams of sodium nitrate in sufficient water in a 300. mL volumetric flask, and then adding enough water to fill the flask to the mark. What is the weight/volume percentage of sodium nitrate in the solution? Weight/volume percentage = %

pour it 2. Still sleepy from a late night studying, you take the milk out of the refrigerator and pour it on your lemon juice to milk to make paneer (fresh cheese). As a group, craft a chemical explanation for the fact of coagulated milk onto your cereal. The last time you saw milk coagulate like that was when you added breakfast cereal. Unfortunately, by the time you notice the funny smell you have already poured clumps lemon juice to milk to make paneer (fresh cheese). As a group, craft a chemical explanation foea added that spoiled milk coagulates.

Choose the one correct or one incorrect statement regarding the technique of weighing by difference:      the weighing beaker should be moved with a strip of paper used as a handle or strap      preparing 4 samples requires only 4 weighings      the balance should be tared after each sample is removed from the weighing beaker      the weighing beaker must be clean but does not need to be dry      the receiving flasks must be both clean and dry before weighing begins

Bottled orange juice drinks have a sucrose concentration of 23.5 g/100 mL. What mass of sucrose is present in a 750 mL bottle of orange juice?

An aqueous solution of sodium hydroxide, NaOH , is made by dissolving 15.6 grams of sodium hydroxide in sufficient water in a 500. mL volumetric flask, and then adding enough water to fill the flask to the mark. What is the weight/volume percentage of sodium hydroxide in the solution? Weight/volume percentage = %

6. Suppose you start with 100 mL of a 5% (5g/dL) sucrose solution and dilute it by adding 300 mL of distilled H20. a) What is the total volume of the new solution in mL? b) What is the sucrose concentration of the new solution in mg/dL? c) How many grams of sucrose are contained in the total volume of this solution?

A chemistry student must write down in her lab notebook the concentration of a solution of sodium hydroxide. The concentration of a solution equals the mass of what's dissolved divided by the total volume of the solution. Here's how the student prepared the solution: • The label on the graduated cylinder says: empty weight: 8.200 g • She put some solid sodium hydroxide into the graduated cylinder and weighed it. With the sodium hydroxide added, the cylinder weighed 45.74 g- • She added water to the graduated cylinder and dissolved the sodium hydroxide completely. Then she read the total volume of the solution from the markings on the graduated cylinder. The total volume of the solution was 24.09 ml. What concentration should the student write down in her lab notebook? Be sure your answer has the correct number of significant digits. ml

4.  A solution is prepared by taking a clean and dry 50.00 mL volumetric flask.  Some sucrose (Mm 342.2 g/mol) is added to the flask with the following mass measurements recorded: mass of empty volumetric flask:  142.88 g mass of weighing dish + sucrose: 29.83 g mass of weighing dish after adding sucrose to volumetric flask: 24.62 g Some water is added to the flask, the solution stirred until all the sucrose is dissolved.  Then water is added carefully to the mark on the flask.  The filled flask is then weighed again. mass of filled volumetric flask:   187.30 g What is the mole fraction of water?  Answer to 3 decimal places.