Recognize that this is a double replacement reaction in which ion pairs will switch. After reaction, copper (II) will now be paired with sulfate, and sodium with flouride according to the (unbalanced) equation below. Remember that sulfate has a charge of -2, and flouride of -1.

Silver (I) nitrate is AgNO₃. Recognizing this allows us to eliminate two answer choices, which incorrectly substitute nitrogen (N) for nitrate (NO₃) or balance the molecular charges incorrectly. Of the two remaining choices, only one is balanced correctly.  

Since the reaction takes place at STP, we can convert liters of hydrogen to moles using a constant.

Using this value, we can find the moles of carbon monoxide produced and convert to molecules by using Avogadro's number.

To determine which method will produce more hydrogen molecules, convert equal masses of each reactant into molecules of hydrogen gas. The conversion requires us to convert the initial compound to moles, multiply by the molar ratio from the reaction to find moles of hydrogen, and multiply by Avogadro's number to convert to molecules.

Dividing these solutions, we see that the methane method produces roughly eight times the amount of hydrogen molecules.

In order to identify an excess reactant, we use stoichiometry to convert atoms of iron to mass of steam.

We have of steam available, but only require  to fully react the given iron. Iron is thus the limiting reagent, since it will be fully consumed first.

There will be  of excess steam.

First, write a balanced equation for the reaction.

Next, convert 10g BaCO₃ to milliliters of NaOH.

We will be looking for a solution that results in one mole of potassium chloride per ten liters of water.

We will need to find the molecular weight of potassium chloride.

In order to get the desired concentration, we will need to add one-tenth of this amount to one liter of water.

Our ratio, then is:

The only answer to follow this ratio is of potassium chloride in .

This is a stoichiometry question requiring us to convert between grams, moles, reactants, and products.

Use the periodic table to find the molar masses of the two compounds in question.

We can use the reaction formula to find the ratio of aluminum chloride to silver chloride. In this case, the ratio is 1:3.

Now we can set up a calculation to convert grams of aluminum chloride to grams of silver chloride, making sure that all units cancel appropriately.

The question asks us to consider water scarcity. Assuming our goal is to utilize minimal water to produce maximal hydrogen, the natural gas method is most efficient as is produces more hydrogen per mole of water consumed.

One mole of water produces three moles of hydrogen.

Four moles of water produce four moles of hydrogen.

Find the volume of hydrochloric acid (HCl) needed to react completely with 5.6g of manganese (Mn).

Since we only need 85mL of acid to react with 5.6g manganese, we have an excess of 565mL hydrochloric acid, and manganese is the limiting reagent.