How many moles of helium gas are contained in a 4.0-L flask at STP?

A student did an experiment on the cycling of environmental gases. She placed water and bromthymol blue in each of four test tubes. No other items were placed in tube 1.

In the reaction 2co (g) + o2 (g) → 2co2 (g), what is the ratio of moles of oxygen used to moles of co2produced?

A model of fossils formed on land, on the shore, and in water was set up in Ms. Bill's classroom. One of the students commented that the model gave her the wrong idea about the types of fossils found in each location.

In 1994, the trade deficit was over 150 billion dollars. True or False?

As the temperature of a sample of a radioactive element decreases, the half-life will a) decrease b) increase c) remain the same d) none of the above

Which of the following is a cost of recreational activities? A. Exercise B. Economic growth C. Noise D. Social interaction

There are three ways that heat can move from one place to another. Use examples pertaining to how heat is transferred from the sun to Earth and in the land, ocean, and atmosphere to explain all three.

What is temperature? A measure of the kinetic energy of a system. Energy of a system. How hot something is. A measure of density.

How many molecules of sodium nitrate are produced when 17 g of sodium azide, NaN3, react according to the following equation: NaN3 (aq) + AgNO3 (aq) - --> AgN3 (s) + NaNO3 (aq) Question options: 3.7x1023 1.6 x 1023 1.85x1023 6.02x1023

Which statement is true for the given reaction? Zn + PbSO4