Chem Lab Final

What is a meniscus? Why do some liquids develop a menicus? How do we read the liquid level in a volumetric measuring device in which a solution forms a meniscus?

A meniscus is a curve of the liquid, at the top. Liquids develop a meniscus when the liquid is attracted to the container or the molecules have a stronger attraction to each other than the container. Read from the top of the line for accurate measurement

What does it mean to say that density is a characteristic property of a pure substance?

All samples of a substance have the same density, even if they are different sizes.

Define density

Density is the mass contained within a unit volume of space of a sample and represent a ratio of the mass of any size sample divided by the volume of the sample.

What is the difference between the density of a solution and its specific gravity?

Density is the property of matter that can be defined as a ratio of mass to a unit volume of matter and specific gravity to measure density relative to the density of a reference substance. Density is measured in units whole specific gravity is a pure number.

Why is it important to use the same balance when making several mass determinations of a given object?

If a different balance is used, it could end up having the wrong measurement. Each balance could be calibrated differently

What error would be introduced into the determination of the density of the irregularly shaped solid if the solid were hollow? Would the apparent volume of the solid be larger or smaller than the actual volume? Would the density calculated be too high or too low?

If the solid was hollow then it would cause the mass to drop and the volume to be too high. Since the density is mass divided by volume, the density will be too low.

Why is a rubber safety bulb always used when measuring volumes with a pipet?

It is used as a vacuum to draw liquid into the pipet

What indicator will be used in the acid base titration experiment? Why is this indicator suitable?

Phenolp

Three natural sources of calcium ion that should be included in the diet.

Seeds Beans Almonds

When determining the density of a pure liquid or a solution, the temperature of the sample much be measured. Why does the density of a liquid sample depend on the temperature?

The density of a liquid will often vary with temperature

Why should liquids never be never be poured or used in the vicinity of a balance?

The liquid can ruin the results of the mass by getting into the balance

When determining the mass of an object, first determine the mass of an empty container and then add the object of interest to the container and determine the mass of the container with the object of interest in it. Why is this method used?

The mass of the container is known and can be subtracted off the mass of container and object to get just the mass of the object.

What error is introduced into a mass determination if the object being weighed is not at room temperature?

This is a weight error which is caused by warmth/heat causing the air around it to rise, making the mass less.

Explain: "weigh approximately 5 grams of NaCl to the nearest milligram

This says that the nearest amount to 5 grams of NaCl should be weighed. The amount should be weighed with some difference in milligrams which is the approximate value nearest the 5 grams.

Why is it important to keep a balance clean?

To reduce the risk of contamination which would make the mass incorrect

How do we know when the inside of the barrel of the pipet or buret is clean enough for use?

Water will flow in sheets down the inside surface without beading up anywhere

Although the absolute masses of Beaker A and Beaker B were different, you were able to determine the correct masses of your two unknown objects using either beaker. Explain why.

We were able determine the correct masses of the object because we measured the mass of just the beaker without the object in it. Then subtract the mass of the beaker and the object from the mass of just the beaker to find the mass of the object.

Explain the difference in mass and weight

Weight is the force of gravity and the mass is the actual amount of material contained and measured

Define an indicator

natural or synthetic dyes that exit in different colored forms at different pH values