In your chemistry lab, you mix baking soda and vinegar in a beaker. You carefully find the mass of the baking soda and vinegar you use in the reaction. However, after you are done with the reaction, you find that the product of the reaction has much less mass than the combined mass of the reactants. Evaluate your results. Are they correct? How might you perform this reaction again to make sure?

A group of students working on chemistry homework calculates the equilibrium constants for three reactions. Reaction 1 has $\Delta G^{\circ}=-50 \mathrm{~kJ}$, reaction 2 has $\Delta G^{\circ}=-30 \mathrm{~kJ}$. The students are surprised when their answers for each reaction are very close to $K=1$. Suggest what error the students must have made and calculate the actual values of $K$ for these reactions.

Recognizing Action Verbs.Underline the action verb in each sentence. Then label each as visible or mental. The receiver barely caught the ball.

A turning point is a place where a graph changes direction. Suppose you start hiking north on a winding trail, and the trail makes a turn and heads south, and then north again. If you make a total of 3 of these 180 degree turns, in which direction will you be hiking after the last turn?

As the weapons officer aboard the Starship Chemistry, it is your duty to configure a photon torpedo to remove an electron from the outer hull of an enemy vessel. You know that the work function (the binding energy of the electron) of the hull of the enemy ship is $7.52 \times 10^{-19} \mathrm{J}.$ If the hull of the enemy vessel is made of the element with an electron configuration of $[\mathrm{Ar}] 4 s^{1} 3 d^{10},$ what metal is this?

Use mental math to find each percent of change. Tell whether the change is an increase or a decrease. from 25 to 30

Classify each of the following as an observation or an inference:
a. Bubbles are produced when baking soda solution and vinegar are mixed.
b. Baking soda solution and vinegar react when mixed.
c. The dog with muddy paws has been digging in the garden.
d. Katie was late to chemistry class on Wednesday.
e. U.niversal indicator turned red when added to hydrochloric acid.
f. Universal indicator showed that hydrochloric acid is acidic.

In analytical chemistry, bases used for titrations must often be standardized; that is, their concentration must be precisely determined. Standardization of sodium hydroxide solutions can be accomplished by titrating potassium hydrogen phthalate ($KHC_8H_4O_4$), also known as KHP, with the NaOH solution to be standardized. a. Write an equation for the reaction between NaOH and KHP. b. The titration of 0.5527 g of KHP required 25.87 ml of an NaOH solution to reach the equivalence point. What is the concent ration of the NaOH solution?

Percent error calculations are used to determine how close to the true values, or how accurate, experimental values really are. The formula is similar to finding percent of change.Percent Error = (Experimental Value - Actual Value)∕(Actual Value) x 100, In chemistry class, Charlie records the volume of a liquid as 13.3 millilitres. The actual volume is 13.6 millilitres. What is his percent error? Round to the nearest percent.

Helena works in a chemistry laboratory. Due to equipment failure, she may have inhaled toxic fumes. Five hours after the incident, a blood sample shows a toxin concentration of

$$0.01006 \mathrm { mg } / \mathrm { cm } ^ { 3 }.$$

Two hours later, another sample detects a concentration of

$$0.00881 \mathrm { mg } / \mathrm { cm } ^ { 3 }.$$

Assume that concentration varies exponentially with time. Write an exponential function to model the data.

Recognizing Action Verbs.Underline the action verb in each sentence. Then label each as visible or mental. Elizabeth Kenny developed a treatment for polio.

The following quote about ammonia $\left(\mathrm{NH}_3\right)$ is from a textbook of inorganic chemistry: "It is estimated that $26 \%$ of the hydrogen bonding in $\mathrm{NH}_3$ breaks down on melting, $7 \%$ on warming from the melting to the boiling point, and the final $67 \%$ on transfer to the gas phase at the boiling point." From the standpoint of the kinetic energy of the molecules, explain (a) why there is a decrease of hydrogen-bonding energy on melting and

Althea measures the following volumes of water in millilitres in beakers in a chemistry lab:

$$\begin{array}{llllllll} 210 & 215 & 235 & 208 & 210 & 218 & 218 & 215 & 208 \\ 230 & 210 & 218 & 218 & 205 & 202 & 206 & 224 & 225 \\ 207 & 215 & 210 & 228 & 230 & 238 & 234 & 201 & 210 \end{array}$$

Which measure of central tendency best describes the most commonly measured volume of water?

Chemistry A large vat contains a solution that is $30 \%$ salt and $70 \%$ water. Eight kilograms of the solution are removed from the vat and placed in an open container. After $2 \mathrm{~kg}$ of water evaporate from the open container, a lab technician takes an additional 2 kilograms of solution from the vat and places it in the open container. Now, What percentage of the open container's contents is salt?